You'd be surprised. Car wash, barbers, boot sales, market stalls, charity collections, church collections, anywhere that the network or card machine is broken, village fetes, school fetes, church fates, collection boxes, people that have lost their phone or bank card.
More than you'd think to be fair. Lots of older people still rely on it, and homeless people might not necessarily have a bank account or a working debit card to use at a checkout.