The Problem With Support Popularity Is Not Riot's Fault
Riot has been pushing so hard to make supports as fun to play as other lanes for ages. Prior to Season 4, support were the most gold starved position by a humongous amount, and everything was based on base values and base utility, unless you were gods of bot lane (Piglet and Manduh come to mind). They have made strides to make supports not just a well fleshed out position, but a fulfilling experience.
The problem is us, simply put. We crave the insane outplay kills, the pentakills, and not the amazing support moments. Very little of what supports do is considered flashy unless you are playing Thresh. They don't instill a "wow" factor. They take a lot of game knowledge to master, but few of them require intense mechanical skill that you see in other positions. Supports are simply incapable of carrying a team to victory, as they can only support.
the reason this champions playrate will never be low