I don't have any reason to trust that a VC-fueled monster like Spotify understands this. If Spotify bought Bandcamp, I would remove my music from it.
VC-fueled behemoths like to make people dependent on them. I can't trust my business to a company that gets most of its money from outside investors instead of the people who use the service. Their incentives are fundamentally misaligned with my interests.
Often these are people I've sent from somewhere else, and we talk regularly. It's not like with Facebook where it's a faceless corporation unless you're spending enough on ads to get an account specialist.
They generally knew me before they gave me money. I'm not collecting any data on them other than the email. I don't even run analytics on web pages I control. I wouldn't even know what to do with it that would tell me anything I don't already know, or that I couldn't get by just asking.
Bandcamp is maybe one of the few examples of a service/shop that actually benefits artists and fans. Having them bought out by some VC tech behemoth will almost certainly see their offering ruined.
Bandcamp's site loooks like it was designed by a schizophrenic person.
A lot of music sites in general seem to prefer form over function IMHO.
Discogs.com is a notable exception of course.