15-20 years ago when I was still touring, custom IEMs were the defacto standard for drummers, at least the circles I was in. Crazy expensive, but absolutely worth it if you cared at all about a solid mix while you're playing live (and also value your hearing).

I imagine that a ton has changed since then with respect to quality of consumer-grade earphones and I don't have a great frame of reference for that anymore. But I do know many live audio folks, drummers, and other touring professionals still using IEMs, that could be as much habit as utility though.