the biggest problem (like anything else that involves fiat) is all the problems that the fiat world brings with itself, starting with needing a license to install one in real world.
It's impossible not to pay attention to unfortunately. The laws aren't just strict to crypto to fiat ATM's, but also those that allow you to convert crypto to crypto. Governments have made it their top priority to figure out who each buyer/seller is so that they form a risk analysis and see if you are paying your taxes and whatnot.
We might even get to a point where banks will be competing with crypto businesses and upgrade their legacy ATM's to offer people the ability to buy and sell Bitcoin. The battle for the fees will be immense. Banks know they can easily gain an upper hand. KYC/AML isn't needed because they already have your information. Convenience wise this is going to be a killer service.
I've read somewhere that some regural ATMs (operated by banks) already let you buy bitcoins, and the ATM will print a QR code with the keys of a bitcoin address where it loads the bitcoin you buy with your debit card. I don't know in which country you can find these ATMs but a quick google search could help.
Interestingly, there's no other way, they don't let you sell bitcoin (I don't know why, if you are already identified with your debit card, so KYC won't be a problem).
Maybe the problem is that it needs more technical stuff inside the ATM to be able to receive bitcoin and to exchange it, but if it works the other way, there should be a solution for this too...