Sure, but there IS such an ecosystem. For example, for 3D, there are sites like ...

wly_cdgr on July 14, 2022 | parent | context | favorite | on: It’s time to make that indie C# game in Godot

Sure, but there IS such an ecosystem. For example, for 3D, there are sites like TurboSquid, which shows up on the front page of a Google search for "3d model asset store"