0.x is not that you don't want people depending on it, you just don't want them to come and complain when you quickly introduce some breaking changes. The project is still in development, it might be stable enough for use in "real projects(tm)", but it might also still significantly change. It is up to the user to decide whether they are OK with this.

1.x communicates (to me at least) you are pretty happy with the current state of the package and don't see any considerable breaking changes in the future. When 2.x comes around, this is often after 1.x has been in use for a long time and people have raised some pain points that can only be addressed by breaking the API.