Not sure when it changes, but the usual explanation (by Americans themselves) of this US-only remote thing is that they afraid of dealing with the people who are not easily suable.
In our case, the explanation is even simpler. Most of our work is for local devs, where the clients prefer to be able to meet the freelancer face-to-face occasionally. Even for a project where most of the work will be done remotely, kick-off meetings and in-person collaboration is still valuable.
Of course it is valuable, but why limit the choices a priori? Let your clients choose by themselves, maybe some of them will prefer to sacrifice face-to-face meetings in exchange for finding the best candidate...
In general, with marketing, you need to keep your Message simple. As in drop-dead simple. Especially when you're veyr small.
That's why you see food trucks offering tacos, sushi, or organic chocolate-and-truffle-oil-suffused hempseed brownies, respectively... but food trucks offering all 3 of these, not so often.
With recruiting it's kind of the same. Also, out-of-towners have different filtering / recommendation / communication needs, and take different payscales, also
So they're probably just applying the 80-20 rule, and catering to what their known client base seems to ask for most.