Neat product! I'm a novice in this space but I'll definitely keep eyes on.
On adoption.. I think your hunch is at least part of it. I think another part, one that is very solvable, is there are not a whole lot of instructions for DIY hardware & software setups out there.
My impression is most AIS hobbyists use kits & proprietary hardware shipped from commercial providers (eg MarineTraffic), while rtl-ais is pretty obscure. Documenting what I can as I go to change it.