It's certainly not your only option. Cash App is just one way you can set up Apple Pay without a credit card. There are other debit card apps you can use, but you don't have to use a debit card at all. Apple's own Apple Cash lets you send and receive month with Apple Pay. And of course, you can use Apple Cash to send money in the Messages app, which doesn't require a debit card. Additionally, parents can use Apple Cash Family to send money to their kids.