Why doesn’t every nostr client integrate a wallet?

What advantages does a client have that doesn’t have one built-in?

I want to zap newcomers using #introductions, yet it seems few and far between being able to actually zap those newcomers who have to learn about setting up a wallet if their client doesn’t have one built-in.

Wouldn’t having it already built-in improve UX for all involved?

Could you allow a toggle to not receive zaps if a newcomer so desired?