Awesome comics.
There have been plenty of points to this issue.
In my opinion the root cause of this issue goes all the way back to Riot and how they designed League. Today there is little argument that while winning a match has nothing to do with KDA, Riot has built a game thats built around KDA. What I mean is this. In League the largest game wide popups for "GJ / pats on the back" are all completely kill related. In league there is no popup for an "assist streak!" its all about kills.
Let's talk about kills for a moment. A kill in league just means you got the last hit and dealt the last 1 damage that ended up killing the player. Others could of set up the situation, done the other 99.9% damage, but you did the .1%. So with Riots (flawed) system, you get the game wide alert. Same thing with kill streaks. All you did was get the killing blow. You didn't do anything else. No one in any real game can 1v5. If you get a multi kill chances are there was at least 1 other person on your team involved. But Riot fails to recognize their contributions and instead chose to just focus on the killing blow. Riot created a selfish system that's completely built around kills.
You get the notification for the kill. in game when you open the players view, you see KDA front and center. In the post game window. Again you see KDA front and center. Riot preaches that the game is not about kills. That it is about objectives, working as a team, and eventually hopefully winning. Yet their game system is completely built around providing players with some form of satisfaction and recognition for kills only. Sure pros are better and know when to get the kill and when to not go after the vayne last hitting in the bot lane by herself when you could push and take an inhib instead of chasing her. Yet way to often someone or some people go after the Vayne.
If your team works together and kills the dragon or baron. You get some terrible yellow text in the chat box. If you have 4 people working to push a tower. You don't get anything. If you are in lane and your bot lane kills the enemy, your ADC (hopefully) gets a game wide alert saying "duo kill!".
Their game is completely built around recognizing killing blows. It is not built around recognizing teamwork and objectives. It all again comes down to practice what you preach. If you watch the LCS, you never see Phreak getting super worked up about how a team worked together to take an objective. He uses his normal voice for that. Suddenly throw in a fight and someone gets a penta kill? Watch and Phreaks voice and volume climb like a rocket. He will likely be standing the next time he is on camera. Again the system is built around the killing blows of one champion even though there were plenty of other teammates involved.
So once you understand that Riot has built a game which puts killing blows on a pedestal, that does not recognize teamwork or cooperation, then you can see why people don't play support.
If your ADC gets a kill in the bot lane, your ADC more often than not, did not 2v1. Your jungler or your support made a play and you capitalized on that. The support is not recognized for their contribution to the team.
When you build a game that only rewards and provides recognition for kills and does not reward or recognize players who contributed to kills, or objectives its easy to see why A. No one plays support. (because you are not recognized for your contributions. Either by Riot and the game, or by your team) and B. They want to feel recognized, that someone out there will notice that they are contributing to the team and that the rest of the team knows it. Instead it's through killing blows. This right here is the reason you see some supports taking CS or "accidentally getting the killing blow" (P.S. It wasn't a mistake)
This is why people play ADC, why they play mid. People want to be the one to get the kills. Not because kills mean you win, but because League rewards and recognizes kills. That somehow your KDA means you are amazing. Everyone wants to see their name up there with PENTA KILL! Its just a failed design and it's really easy to see why the community judges the performance of one another by kills and deaths alone. You die 3 times in lane? The general response "Man you are terrible" look at that he has a negative KDA. The reason doesn't matter. You have a negative KDA you are obviously terrible. That's the game they made.
It is 100% on Riot and how they have designed league over the last 6 years to understand how we got here and how people are 100% kill focused for the most part. Sure some people will realize the clear objective when it counts, but everyone wants their name in lights. They want to feel like they are the important one responsible for the victory. Riot's League provides that.
So again it is really easy to see why people don't like playing support. Simply put, you are never recognized for your contributions. You have an assists percent of 100%? You were involved with every kill your team had? Nothing. Not a peep. Your ADC does poorly? You are immediately blamed. "he is the ADC super carry amazing player with the god complex! he can't do anything wrong." He goes in for a poor trade and dies? "why didn't you support me?". Enemy jungle comes in over a wall for a gank "Why didnt you have a ward there?" It is _always _ the supports fault. If you ever find an ADC who recognizes their own mistakes and carries them on their own shoulders. Friend them. You just found a freaking 4 carrot diamond in the ocean.
TLDR: Riot created a game that is "supposed" to be about teamwork, taking objectives, and working together for a victory. Instead they created a game which only provides recognition for kills. Their game keeps KDA front and center. The champion screen? CS and KDA. Post game? KDA. The game only provides recognition for kills. It does not recognize all the other people who participated in that kill or set up the situation much less the whole point of the game which is to work together as a team, take objectives and hopefully win. Sure we got the "assists" tally, but again it is not recognized in game. Just the killing blow. The community is focused on kills because that's the game Riot made. Kills and Deaths are the stats Riot force feeds us. So we natually use them as a way to judge another players performance. If you didn't get the killing blow, but did the other 99% of the work. Riot doesn't care. They don't give a shit. Teemo got the killing blow and thus gets his name in lights! Riot provides virtually no recognition for taking objectives or the contributions people made which ultimately (hopefully) lead to your teams victory.
Its like we are playing CoD and you are 100% focused on your KDA and the player with the most kills is your teams best player. Except its not team deathmatch. Its capture and control with infinite respawn. Kills don't mean shit. Boom.