i think that since you are comparing apples to oranges what about instant messaging clients on phones

sure, most of them use servers

but keet.io you only need to be running the client on your desktop and it picks up your messages and your phone can grab them too

for group chats anyway, i don't think they have (nor simplex) made it easy to share identities but with nostr i could do that tomorrow if i could throw together a quick GUI for a nostr chat client, it's beyond easy on the protocol level

i just osted a screenie of my relay's current memory usage, it's less than an average web app

so yeah... actually, things have progressed a long way since it was necessary to have hosting to run peer to peer services