Only because of company culture, in most enterprise projects I work on, doesn't matter the stack, everything gets legal and IT approvement into the internal Nexus.
Devs might do whatever they feel locally, however if those files are going through CI/CD their dependencies better be in Nexus.
The average Java dev will try to reach for Artifactory/Nexus much sooner than the average Python/Ruby/PHP/Javascript/... dev, in my experience.