Why does Riot Keep reworking champions that don't need it?

While I can agree that some champions need major reworks to regain relevance in LoL, some reworks are just not necessary. I think Riot likes to rework champions (fiora, poppy) that are big on 'make or break' gameplay. If they get ahead, they dominate. If they struggle, they get left behind. In my opinion, this feature is all a part of the game. High risk can lead to high reward but is also able to bring your downfall. Riot continuously tries to 'balance' champions and it almost seems like it is just in hopes that they can become relevant in LCS. The actuality is that not all league players are LCS level. In different ELOs, different champions shine. Please stop reworking champions that dont need it.