Lack of users, investment and too many competing distros were all given in the early days of desktop Linux as reasons why it was simply not worthwhile. The thing is, this phase of development, where some devices exist that only nerds play with for a while, is necessary for there to ever be a mature Linux mobile UX. When you buy one of these devices you're not buying a Linux phone, you're choosing to participate in the process by which a Linux phone becomes a reality. And that process is picking up steam, Ubuntu tried it, many people have run Linux on their android devices with unlocked bootloaders, but pine (and librem and others) have actually created a market environment where things are actually advancing, and in my opinion advancing much faster than desktop Linux did.