I think part of it is that, in the US (and probably in many other countries too), the roles of maker and consumer tend to be more clearly separated. In contrast, among Japanese users, that line feels much more blurred.

One thing I’ve noticed is that there are a lot of “avatar worlds” where people just go in and pick premade avatars, but these are almost nonexistent—or at least not widely used—by Japanese audiences. The main exception seems to be worlds specifically designed for trying on sample avatars, rather than adopting them as-is.