In thoery, yes.  In practice, no.

A relay is a web server, which offers specialized services.  It's harder to run a relay than it is to run a web server.  It's harder to maintain too.

Some will do it, but most will not.  Indieweb had a dream of everyone running their own web server.  I support it in principle, and I do so myself, but it just didnt take off, because people are lazy.  After decades, a handful do it, but it's never going to become significant.  Even the nostr relay network is heavily dependent on damus, which I think is a company.

So while they might not get everyone, that is never the goal.  The goal is to get the vast majority.  They will deal with the exceptions if they become a squeaky wheel.