Your have to ask the devs. I think right now they are doing it for ideological reasons, not to make money. There is certainly a market for someone to come in and create a high quality paid app when nostr grows larger, but right now I think they are just trying to bootstrap growth in the protocol because they believe in it.
Discussion
Mmmh, I do not think a paid app is a good solution here. I could imagine some apps or relays would have in it ads (of course nobody wants them).
Or they just rely on earning enough on running a paid relay 🤔
This is not really clear to me.
