I think form factor and reliability account for a lot... I've tried using other arm boards, and they just haven't been as reliable in terms of support/drivers/reliability as the RPis have been in general... With the inflated pricing, I've actually just jumped up to the tiny intel systems, since I'd usually be getting a separate enclosure and ssd anyway. I can see others going to esp32 if their original use was a bit overkill, if easier to work against.