Why do some ATM machines require that you do ridiculous proof of identity tests such as: ID scan, fingerprint scan.. what the hell?
Why others only require SMS?

If you put too much hassle in the machines to do the transactions, it will all fail.

Some operators don’t require full ID at small purchase levels.

If an operator wants to risk it and go with a low friction AML strategy, they are likely to do so without being banked. Banks are going to want to see an operator’s AML policy before choosing to do business with them. If they see your policy as weak, you don’t get a bank account. Without a bank account, you can’t wire dollars to the exchange where you replenish your inventory of bitcoins. That means you’re limiting your access to bitcoin inventory which usually means higher prices.