[mechanical_fish]

I think hiring existing developers and training them up is a fine plan. And a lot of companies do just that.

But it works best if you have an existing team, trained in the technology, of sufficient size that it can afford to spend a little time mentoring, and with a long-term outlook.

There are teams like that who use Rails. But, as it happens, Rails is also a favorite tool of brand-new startup teams who are already critically overworked and who probably won't be around in six months. And it's a favorite tool of one- and two-person teams: When a one-person team loses a developer, the new hire has no mentor available. So there's plenty of openings for pre-educated Rails developers.

Mind you, there's also the cynical explanation: It's more "efficient" to advertise for "rails devs" because you can screen the resumes so much faster. Those who can't answer trivia questions about ActiveRecord syntax are out! This would, of course, be dysfunctional. But the whole job-ad system is already so dysfunctional that this particular bit of dysfunction may be lost in the noise.