For me, it honestly depends on the nature of the magic in a given setting. In D&D (and most D&D-derived settings) there's little to no consequence or downside to using magic so, sure, I think most people would use it, given the opportunity. But you get into settings like the Old World (WFRP), Melnibone (Stormbringer), Hyborian Age Earth (Conan RPGs), etc and, suddenly, magic is a wild and dangerous thing that not only could screw you pretty bad if you practice it, but it's usually linked to the forces of chaos or evil. In these settings, it makes a lot of sense for heroes to eschew its practice.
Sure. And the first part is why I prefer every class to have magical options, even if the concept of the class isn't "inherently" magical, like the fighter and rogue, and the rest is why I've tried to get conversations going in the past about making the Paladin, Bard, and even Cleric, not spellcasters as a variant option.
I've seen really wild takes where only the wizard ends up with spells, as such, or at least the only one with a big spell list and the spellcasting feature, while others might have a class feature that lets them cast a specific spell a few times or whatever as a shortcut to their concept, but most of their iconic spells would become class features instead. I think there would be merit to exploring that idea, even if I don't think I'd play a game using it.
What I think might be useful in my own game, and in DnD games in worlds like Eberron, is to figure out some
benefit to eschewing spellcasting that is actually worthwhile to pursue.
A lot of that comes down to countering magic, tbh. Anything else I can think of end up making magic have downsides, instead.
So like, if a fully mundane warrior can interrupt spells more easily than someone whocan also cast spells, that's a potentially fun benefit to being fully mundane, and in dnd that can mean "no spells from class or feats, excepting racial feats" so that forest gnomes can be anti-magi as well. Stuff like monk abilities that aren't spells, barbarian "magic", etc, wouldn't count as non-mundane for those purposes, because they come from within and don't interact with the weave necessarily.
In my own game with magic skills in a modern world with hidden magic, that could simply mean you can't have ranks in a magic skill that don't come from your ancestry if you want to have bonuses to countering magic. Perhaps I could add a skill to either the Physical Skills or Interaction Skills groupings for shutting down and resisting magic, though that would make it the only skill you have to meet prerequisites to take a rank in.