It's kind of alien to me too, the idea of being someone's friend being taken as a social rejection (which more often than not means no longer talking to that person) because no le sexy sex will occur.

Yes, it's disappointing when someone doesn't reciprocate romantic/sexual attraction. For me the alien part is "therefore cut that person entirely out." If it wasn't intended to be a hook-up all along, it makes the entire social bond seem sus in hindsight to me.

In my experience, actually accepting a non-romantic friendship often results in additional friendships with that friend's friends if that friend actually likes you non-romantically, and sometimes those can bloom into romance anyway, often at the first friend's encouragement/recommendation. Don't do it for that reason (transactional thinking is a fuck) but my point is that fatalistically seeing "the friend zone" as some evil bad thing is self-fulfilling prophecy.