I disagree that PayPal is good enough. To receive money via PayPal you have to link your bank account which takes verification and can be a PITA. Square Cash "refunds" it directly to your debit card. You just type in the number. It's also usually easier than using your bank's EFT interface to send money.

However this debit mechanism is also what makes it so expensive for Square to operate (>20 cents per transaction in interchange fees).