libertarians, BTC-guys, privacy... these guys are here due to quality, not quantity. 
when they want to reach a broader, normie audience, or sell stuff, they go to Big Tech social networks. 

Another point: nostr does not even have reliable reach measurements. 
if a vendor can not know how many views, clicks, etc, his posts generated, he can not estimate their worth. 
posting is worktime for them, there are not here for the info.