Tough to onboard people if the only way to enter is by already being onboarded.
Also, many would prefer to pay in paper than to lose their BTC
Discussion
So u should be able to do either then
Not just fiat
nostr:npub1t8a7uumfmam38kal4xaakzyjccht4y5jxfs4cmlj0p768pxtwu8skh56yu