relays are web servers, with the storage turned off

flick a switch and you can turn storage back on

you shouldnt store things in the RELAY, because it was just designed for text strings aka notes

but all web servers have the ability to store stuff, that is, in fact their primary purpose

a relay is a web server, with an extra function, namely realtime updates

tl;dr web servers can do many things, they can store files, they can relay notes.  But dont use the relay notes part to store files.  Use the built in file storage part to do that.  That could be a home server.  And then you can route to it via your npub.  But homeservers can live anywhere, they dont need to be a relay.  And perhaps it's too confusing for most people to run both.