Disclaimer: I’m not an active bk user. I’ve been bk-curious for a while now (Larry McVoy singing the praises of interweaved deltas got my interest), but the lack of “native” packaging has been a roadblocker for me to really try and pick it up.
Packaging has been a long-standing issue, actually, see also “A plan for packaging” that contains a rough roadmap, apparently started by BitKeeper staff. Little is its own kind of big issue. Keeping Windows working seems to be its own separate problem, too.
These issues have been mostly identified for three years, but not yet fully tackled. I think at this point, there’s just an issue with nobody having quite enough motivation to push for it, especially since it’s a relatively intimidating task and you probably have to keep at least Windows, macOS and GNU/Linux happy to start with. Considering BitKeeper, Inc. is effectively retired but has a bit of money left, maybe @mcvoy could be convinced to put up a bounty on this? Packaging is probably a major adoption roadblock for more people than just me.
Incidentally, pure make(1) doesn’t seem to be inherently hostile to packaging. As long as a Makefile handles $DESTDIR, $PREFIX, make install and uses standard pkg-config to find libraries, that should be good enough.