It's probably because high quality 3d is just much more expensive to do. You can easily do all sorts of effects in the constrained environment of a 2d model that take a lot more skill to pull off in 3d.
Plus, ultimately, the anime aesthetic is a 2d thing. It's a lot harder to make a 3d model look good in a 2d art style, as a ton of anime over the years have shown.
Plus, ultimately, the anime aesthetic is a 2d thing. It's a lot harder to make a 3d model look good in a 2d art style, as a ton of anime over the years have shown.