I think that's a big part of the answer to why it hasn't caught among techies. When I tried using it (shortly after release), there were numerous issues in their default apps that nobody could fix because they are proprietary and Jolla didn't seem to have the resources to handle all the bugs.
I'd wager that if it had been open source, the early adopters would have put some time in to fix a lot of the bugs.
In retrospect I'm pretty pissed at them for not being honest and upholding their promises. In my book they're basically con artists that just tried to get the Linux community's money by saying "open source" without actually meaning it.
I later switched to Ubuntu Touch because, despite Canonical picking up the project, the community had continued maintaining it. They could do that because it was freely licensed; nobody could do that for Sailfish.