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Buying bitcoin you just show the machine your wallet qr (preferably a smart phone but a print-out of qr works as well) and then stuff in cash and press “send.”

When selling bitcoin (to a two-way ATM, as above with Leon), you dial up the amount if cashbyou want, the machine provides a qr “address” to send to, you send to address and wait for 1 block to solve usually <10 mins. Then either show the machine the slip it printed, or input the code that gets sent via sms (depending on operating system) and BOOM! The machine soits out fiat dollars. Note: these machines do not run via a bank, nor do they accept bank cards. It’s cash only.
🤩👍

And yes. Tx fee and exchange rate is where the business comes in.

Wouldn't accepting a debit card or something be more useful? Personally, I don't carry much cash, and I'm assuming you can't drop silver or gold into it!

... is it because of the additional overhead that a banking link would incur?

Banks loathe bitcoin. They would never accept the partnership. Cash is the medium between these two currency types.