Ruby has RBS and sorbet to support using type annotations. They are each relatively new and aren’t as clean and well integrated as Python’s implementation, but it’s not as if type annotations in Ruby don’t exist.
It does exist but they are not embraced by the majority of the Ruby community.
Unless type annotations are treated like first class citizen in the language, it won't be good enough. My theory is that those in the community wanting static types went to Go or Rust.
Of course anything can be done with RBS, but I think it came wayyy too late. Python type system is already given time to evolve and survive in the wild.
A second point is IDE support. It is so hard to get started with ruby auto-format, code completion, ctrl-click to follow code and debug. Python is readily usable in pycharm community edition.
Unless type annotations are treated like first class citizen in the language, it won't be good enough. My theory is that those in the community wanting static types went to Go or Rust.