Or just put drives in all your computers and back-up between instead of buying a limited (potentially proprietary) NAS computer just for the purpose and having it being one central point of failure.

I just don't understand the reluctance of people to put storage in their actual computer(s).

HN readers' computers are typically macbooks with extremely expensive and non-upgradable drives.

Because one of the reasons I got my NAS so I don't need to tinker.