i don't think they are really useful either, just a plus for merchant nothing else
The first bitcoin atm that is in Vancoover BC has been tremendously successful. It has been so successful that people would actually go to the coffee shop it is located in to compete with it, and once the ATM's owner got a wind of this, they were able to pay someone $10 an hour to sit near the ATM to fend off people trying to beat it's rates and to educate people about bitcoin (and it still remained profitable).