On this site, people tend to be suspicious of private messages out of the blue from people they do not know.
And when we do receive such a message, we check the person's profile. Can't you understand that some of your post topics would be the explanation for why some people block you? (Women have to deal with all kinds of come-ons here, and they get sick of it.)
The primary form of conversation here , for many of us, is in public.
And I don't think that is a negative thing at all.