Perfectly suitable for daily use, typing from such a device just now. :) IIRC there is a community port for PinePhone as well.
Also they might want to avoid doing business in countries that support software patents and are over litigious over that (eq. USA).
But this limitation is pretty much artificial - the only thing you need to do from the EU is buying the image. This can be achieved via an EU based VPN (reportedly the built in VPN in Opera works) and AFAIK any mainstream payment card will work (does not have to be from an EU country).
Once you got the license and installation image, there are no real EU specific limitations. I have used Sailfish OS twice while on a trip in Japan and all worked just fine - repo access, etc. Also from the download statistics from OpenRepos (a community package repository for Sailfish OS), you can see there is a lot of users from countries that are not officially supported:
That said, the SW will of course lag behind commercial offerings. Just see how long it took for desktop Linux to catch up to the major players. But open source system gives me the freedom to turn it inside-out, get rid of things I don't want (even systemd if I felt really strongly about it), repair what I want - be the owner of by phone and not just a cow to be milked for rent. Nah, I can live without WhatsApp. Or I can get a secondary cheap Android phone for such apps.