Too much risk for less profit. I would never reveal my phone to a nostr client. Phone's are registered by governments.
Discussion
this is why cryptography exists, to do things like this without having to reveal your number to anyone. If you are paranoid about it you shouldn’t use a sim card. Also this doesn’t have to be a phone number, it could be any piece of data shared among friends. Phone # is just the obvious one that is in contact lists.
Sure for cryptography, but still I have to trust the piece of software that creates the hash.