LoL's current roster of supports favors ADCs the most. Take Janna's shield for example; it works best on a ranged AD carry.
Why? Because the shield is less valuable on a melee bruiser and the AD is useless on a mage. There is no reason to support another class when it already goes so well with an ADC's playstyle.
Beerstein1 votesMages just need a different kind of support, maybe Renekton, or some of the more non traditionals you see like Sion.
AlienPrimate1 votesThere are more supports than just Janna. Taric works incredibly well going bot with any melee champion who has a gap closer and CC. Examples would be 
I have personally played Taric bot with Shen quite a bit with great success. Basically if Shen lands his taunt, they will either flash or die every time.
Azadethe1 votesJanna tbh synergizes with top Bruisers more than anything. Adcs generally have enough mobility. Janna with a Darius though can just snowball for days.
doesn't synergize with bot at all..... but I have a 71% win rate with him there..... Why? Because I never lose a turret, can act as a secondary killer, and almost never die.
chipndip11 votesIt's not that they don't outright.
It's that it's painful for melees to lane against a ranged champ in the first place. Laning against TWO ranged champs? Or an Alistar that's free to buck your ass all lane long? HEEEEELLLLLL NO. There's plenty of supports that work wonders off of melee champs, but no melee champ wants to play against the shit that lives in bot lane these days.
Now mages...mages don't have patterns that really need a support to work off of. They have their own engage/disengage baked into their own kits, and how it's pulled off is pretty absolute. They don't need to orb walk to stick to people while whittling them down in most cases because the hit confirm is the death sentence when you're a mage, so you don't really need AA enhancing buffs or MS buffs more than you need someone to get hit by a hit confirm.
