Why pick sona support? wast of opiness

Make as much sens as taking kassadin support. But her mid instead. She is a late game hyper scaling ap midland that get insane team fight presence and can 1 vs 1 any champ at 6 items. She scales so well with elves why she needs to be mid. Her level 16 power spike make permabanned kassadin look weak as fuck. I have been spamming her mid top and adc and got from plat 5 0 lp to plat 2 70 AP in 3 days. Her e is basically perm aoe lulu W late game.