> Of course, you can use checks, but sometimes you need hard cash (e.g., buying a used car).
I use "cashier's checks" [1] to buy used cars, since that still offers more security and convenience (of not handling physically bulky bundles of currency).
A trick I learned from reading sites about how to buy at real estate auctions (where the final price can't be known up front) is to use multiple checks made out to oneself, in varying amounts. The ones needed for payment can be endorsed over to the seller, and the remainder can be re-deposited.
My credit union will send me an effecitvely unlimited number of these through the mail, if they're requested through the automated system and each for a at least some (reasonable) minimum amount.
Still, your point holds. If you need it in a hurry, a physical branch is required.
[1] check drawn on the financial institution, not my personal account