Be Honest: the reason why there aren't so many supports is because it's not a funny role to play.
Why are there so few supports going around Team Builder? Why, in blind pick, do the people hate when they call the role last and they must go supp?
The reason is one, and you all should be honest: Support is NOT a funny role to play. Obviously, this is a game, and even if win is important, people want to have fun, which they have not playing support.
Playing support can be necessary to win, but.. placing wards, waiting for gold and running around botlane, defending a child-like adc, always depressed for mana and that ridiculous damage, sacrificing for allies etc.. there's no fun doing all these things and it's like being a mum. Do mums like being mums? i think not. Do i want to become a mum when i play LoL? No.
Make support role funnier OR more interactive, and there will be a balance among roles, especially in teambuilder.

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he can 1x1 everything who is not overfed, and sometimes even 1x2. And of course, write in allchat "Gems are truly outrageous" after every solokill