I get it. I mean, that's what D&D has generally done in the past. And, it does work.
But, it's making needless distinctions for the sake of trying to make things different. As was mentioned, if we call everything "powers", then people lose their poop and that doesn't work.
Apparently though, if we call everything "spells" it's more acceptable - 10 (ish) years of 5e has proven that. To the point where even non-casters like barbarians and elemental monks get abilities (speak with animals for example) which just reference the actual spell. So, if we're going to give them spells anyway, why not just give them a casting ability, and let the player choose what "abilities" they can do?
IOW, why piddle about with Elemental Monks having a unique casting system that doesn't really work (apparently since everyone bitches about the Elemental Monk) when you can just make them half casters like rangers or paladins, grant them a selection of spells and poof, end of problem. I mean, the Way of the Four Elements Monk is literally (as per the text in the PHB) casting spells. Flat out dropping spells up to and including using the rules for spellcasting. But, instead of just making me a half caster and giving me a selection of spells and let me build my own elemental monk, I have to use this wonky ki system casting that doesn't really work.
There are very, very good reasons for standardizing things. When things are standardized, they work a lot better.