Some projects do, yes. Django, for example, has a library to provide types. In my experience, types are useful even just in my own application, since the librar

Some projects do, yes. Django, for example, has a library to provide types. In my experience, types are useful even just in my own application, since the libraries I use tend to generally only accept simple/fundamental types anyway. Things could definitely be better when it comes to library type support, though, I agree.