Within the few industries I've had a peek at (not hip startups or web companies) this doesn't appear to be that big of a problem. Companies that rely on Python 2 code in the background seem to be sticking with Python 2 without any noticeable penalty or incentive to change. And places that have their core business wrapped up in python seem to be gradually making the transition OK. It's not without cost but you do what you have to do...

This sort of thing isn't uncommon... I see old perl installs behind production software, ancient versions of RedHat, Oracle, etc. and I deal with mostly technology centric companies so that's likely just the tip of the iceberg. Old software doesn't really go away.