You don't have to wait 20 minutes for a Bitcoin transaction to clear for the price of an iced coffee, either. For low-value transactions with a low risk of double-spending you can just verify that the transaction made it into the mempool and is likely to be included in the next block or two, a process which takes seconds at most. It could technically still be reversed during that window but you could just as easily get a chargeback from a credit card, or a bad check. And with Bitcoin you'll have confirmation within less than 30 minutes that the transaction is fully irreversible, vs. 30 days or more with most other methods. Only physical cash offers a faster clearing time.