There's not a lot of applications where bluetooth is essential. Personally, after several rounds of disappointment with bluetooth mice, the only thing I use bluetooth for is handsfree calling and sometimes music in cars. Even that sometimes doesn't work (my spouse's Nokia 7.2 couldn't connect to her car between July and December, because something in the Nokia firmware was broken; worked fine with my car though).

So, my guess is nobody who works on OpenBSD a lot cares about bluetooth on OpenBSD, because they're not using bluetooth much, and don't see any use cases for it that would help them.