Support mains or anyone who ends up in that role:
You have to deal with an exceptionally squishy teammate whose entire role revolves around not building any defensive items, or otherwise they are useless to your team. Even a pure damage Mage builds items that add defensive stats. Furthermore, this type of champion is intentionally handicapped (or so Riot says) so you must babysit them if you ever wanted them to be useful.
You must spend your hard earned gold on a subpar health item to provide vision for your lane. Your lane buddy will then face check every bush that is not warded and your other teammates will not purchase their trinket upgrade. They will also complain you don't have the entire map lit up, as if you actually could do that.
You cannot support anyone else because people and Riot expect the Support to solely babysit the Marksman. Not a Marksman. The Marksman. The role that is always set in stone and subtly enforced by Riot Games. Should you attempt to support someone else, maybe because you have a bad Bottom Lane Marksman, or an abusive one at that, your other three teammates will bitch and moan about the person who Refuses to Communicate.
As for your question, Zwill, new players start out playing the game as an aggressive, Creep Scoring, type of person. They don't get taught how to support anyone, and for a long time, they will simply be sharing the lane, rather than supporting anything (The fifth player who would've been the jungler does the exact same thing at Top Lane).
You don't really find many Support Mains at the lower leagues for this exact reason. You find people who end up as Supports, though.
And why? The Support role is ALL and ONLY about babysitting someone for the first half of the game, 99.9999% of the time a Marksman. The second half of the game, they hang around the team and don't really do much else outside team fights. The only Supports I see that might not have a Marksman as their lane buddy are pre-made groups. Why? Because people bitch if this is not the case. I don't care how much you push the "don't report for off meta" stipulation, people whine and moan if the support does not fulfill these things and babysits the Bot Lane Marksman.
Thee role itself is pretty damn mundane for anyone who is not a true, blue, dedicated support main. Simply put, it's not very fun to rely on passive gold income and babysit a person who is more often than not, stupid AND deliberately fragile. Getting yelled at and harassed for not building specific items or lighting up the whole map is not something people like. Support is like a damned minigame in the game.
I don't care how it's done, but I'll take damage reductions across the board on the Support role if I could influence other lanes, or provide map pressure, or long range utility. I'd be even more happy if the Sightstone was considered an Essential/Recommended item for EVERY champion. Sightstone roaming bruiser or supportive Marksman my foot. Sightstone Teemo ... Do people realize some "Supports" (official, "meta", or off meta) are so squishy that if they go near ward dropping range, they can be insta-gibbed, even with a Sightstone? Others are actually harmed by building health, which derpy dippity do, the Sightstone is built from a health item.
, 
or any other champion that uses Sated Devourer effectively.
mid, or 
bot? Then we need point and click cc... crap. Gotta kick that 
top since they can jump off of Equalizer and hope we get someone like 
or at least 
, I'm in my promos and can't afford to lose this one.
