You don't have to have it on your phone. You _can_ have it on your phone. You could also just put the data someplace semiprivate, like our project team relay, or run a relay on your PC.
Nostr without relays really is just another Twitter.
Discussion
Well, I think I get that idea now, but, it's a big ask for normies, I think.
We're still early days. It'll all be quite seamless.
Even the phone relay setup could just be a button you press in your client, or it could auto-setup, when you install a client. That's probably where Damus and Amethyst will be or are.
Users actually can't differentiate a client from a server, if you make the interface very smooth.