So riot forgot about one of the main problems of supporting you have to deal with
You don't get a lot of the XP you need while supporting.
My fellow support mains know what I'm talking about. Sure not having gold to buy items sucks, but if you support long enough you get used to it. Yes no one gives you a lot of credit and you get all the blame, but as the team's stay-at-home-mom you know you've got a thankless task that needs to be done. Yes some champs are more passive than you'd like them to be, but every time those champs aren't completely passive riot nerfs them back into being passive because everyone in live balance has two butts to poop on your main with... politicians are two faced while game devs are two butted.
However, I think it's the lack of XP that in the end really turns people off from supporting even if it isn't the obvious thing. I mean think about it. As a support, the one thing you really have to scale on is levels and because you are warding, roaming, clearing wards, not CSing, etc you are going to quickly fall behind in levels compared to the rest of the team. A lot of supports can't come back in the level department very easily. Let's say there's a large wave of minions bottom. How many supports WHO CAN'T GO MID have the kits or the damage items to quickly clear a wave to catch up in gold or levels? No many. Even if you did, a support on his own is just begging the other team to pick him off while your team is raging at you to group after you ward the other side of the map by yourself. And when your team is grouped in a lane and CSing, how easy is it for the support to get CS then when you've got an ADC, AP mid, toplaner, and jungler competing for those CS as well? It's not. Plus you aren't getting very much XP when a minion is split 5 ways.
I mean yesterday Meddler, who is a bloody support player, mentioned his thoughts on supporting issues and having to deal with not having XP is so second nature to him he didn't even think about mentioning it. He's so used to being 3 levels behind his team, it didn't even register to him that non-support mains don't like being that far behind people nor do they know how to play well while lacking levels as much as they are lacking items.
Here's why no one supports: you've got to take all the blame unless the jungler pissed off the team, you get none of the rewards, and the one thing you need most to do your job (levels as that's the only thing you have to scale off of) you don't get... because you are busy doing your job. I mean not being able to buy the fun items that make your damage go up is an issue for the non-mains, but as far as the role is concerned doing your job properly makes you miss out on XP as much as it makes you miss out on gold.
Supporting is the only role in the game that punishes a player for doing his job correctly, not just in terms of no GP or fun items, but in terms of no levels as well. Here's a thing about game design that I learned by reading rosewater: players do what you reward them to do. Being support isn't as intrinsically rewarding as some of the other roles in the game. It wouldn't surprise me if a lot of people became support mains only because they like the shorter queue times and they seem to win more in the role more than because they really enjoy supporting. I read a long time ago that in MMOs maybe 10% of the player base tops gravitates to the healer/support classes. Last time I checked, riot needs 20% of its player base in the queue to be either a support main or secondary/fill (also known as support mains).
So if you aren't someone who naturally gravitates towards that role, getting punished by both your fellow players and the game itself is quite a turn off. A lot of players like big numbers. Unless you are counting healing done on soraka, supports don't put up big numbers. A lot of players like getting kills. If you are on support and get more than 1-2 kills, you run the risk of getting flamed by your team. A lot of players want to get a pentakill. Supports are the rarest class to get a pentakill. Players want to do interesting stuff all the time. Supporting means making sure your team has vision when any bush can contain the enemy team and no you don't have enough wards to ward every single bush there is.
Want to push an objective? Supports can't do that alone. Want to clear a lane or the base? Many supports can't quickly CS even if the game depended on it. Want to split push because your team can't win a 5v5? Can't do that on support. Want to sneak/steal a dragon? Supports can't do that... I tried to steal a dragon with sona once because our jungler was AFK, it didn't work out so well.
So not only does the game punish you, you are also extremely dependent on the rest of your team because a lot of the things ESSENTIAL TO WINNING OR SAVING THE GAME that does not involve vision are things support players can't do alone. That's why supporting sucks to most people. You are entirely responsible for vision when half of your team won't look at the minimap but you are completely dependent on your teammates for a lot of the things you need to be able to do to win the game.
More XP won't solve all the problems, but it would take a big one a lot of people don't think about away.
A month ago, I suggested that sightstone give XP to players who are close to teammates with more levels than they are. Maybe riot should consider one of the core support items like sightstone or the GP items give supports XP as well.
with smite and exhaust in the jungle. What mastery or spell would be so support focused that other lanes wouldn't want to use?

go there and you end up with a double standard for champions like

which are commonly accepted, but then you have champions like
to increase shared XP.
