Lots of reasons. Sometimes concurrency is a relatively soft need where you could get by with multiple processes, but it would be nice if the language itself pro

Lots of reasons. Sometimes concurrency is a relatively soft need where you could get by with multiple processes, but it would be nice if the language itself provided some capability for things like threads. Or your dev team is much more familiar with python than with other languages, and the time to retrain and rewrite would be greater than the benefits. Or the rest of the language could have greater issues and you don't want to give up excellent libraries like numpy.