It's not trivially easy to do large payments to another random individual in the US via bank transfers. The check issue is solved by concluding the transaction

It's not trivially easy to do large payments to another random individual in the US via bank transfers. The check issue is solved by concluding the transaction at the buyer's bank. A cashier's check can be issued by that bank to the seller. Since that check is backed up by the bank's own accounts, not subject to the buyer's whims (e.g., they can't stop payment, and the bank will have confirmed that buyer has that amount in their account and debit it immediately), it's as good as cash (well, unless the bank itself is unsound) but safer to carry around.