They enable recently frustrated libs to make connections with more left wing groups. My mutual aid group got a lot of donations and more volunteers at each of the previous No Kings and 50501 protests. We don't collect information of prospective volunteers, and while our group had to submit some info for the tabling application, it's not more than what we submit for finding grants and contained no personal volunteers information aside from the primary contact. I and several others helped run the tables throughout the event without any event organizers having any info about me.

The police, of course, have access to whatever cell info they buy from all events, so I just leave it at home or turn it off.