Interesting. My perspective is pretty skewed as a semi-pro musician and someone who is mostly a recording artist and not a live band/jam guy. I think there are a lot of people who CAN do it all but might be open to collabs with the right person(s). You are correct that the pro market is vanishingly small but if OP thinks they’re making any money off of bassists who could just post on Craigslist I think they’re in for a surprise.