Can "show spell costs" be a default feature?

I didn't know this feature existed until a live-streamer pointed it out, and I've been using it ever since. I feel like most people (except those who play manaless champions like katarina) would benefit from knowing how much mana it would cost to execute their full combo. And I can't imagine a scenario where showing the spell costs would hinder a person's gameplay, so why not just make it standard?