A Bitcoin ATM is not completely anonymous; most machines, if not all, require users to type in their mobile number before they can be able to complete their transaction. I don't actually know if they verify those numbers are completely fake or real. But they are definitely required for verification purposes.
Bitcoin ATM are just like the regular bank ATM and everything related to it are the same. Along side the high transaction fee of up to about 30% by companies. The idea of having to send to a third party wallet is a turn off. Just like the regular bank ATM the malfunctioning system of the atm could affect the smoothness of withdrawal. Some of these transactions ends up been delayed or faced problems that requires the customer service which are sometimes too slow in handling issues.