I like the last bit. Hiring would be a nightmare. Most serious BE dev (myself included) don't have time to learn a new language that I can only use at a handful (or single company). I want the language I spend the most time with to be something I could take to a recruiter (should I need to).

I worked at a place that worked with Delphi, and for various reasons I had to use it exclusively for a few years. No recruiter would touch me. Not until I got some time with Rails did I have a chance to escape.

As a former mobile dev, I'd also like to add, being an app dev vs BE dev isn't just about the code either.. It's a very different way of looking at problems. The skills might transfer, but they're living in different worlds. The language isn't the only obstacle.