It is same as that we make use of the normal ATM. In simple terms it is similar to the trade we make through exchanges. Compared to the past now the use of bitcoin atm services has decreased a lot due to the increased withdrawal fee. People find it better with exchanges, and it has caused removal of lot of bitcoin Atm from different locations.
Not to mention that price is higher there as well. As mostly what they are doing is reselling from one or another popular exchange where you can go and signup today to be able to buy/sell bitcoin. Plus I've also heard that some of them require KYC, image of your password and all that, then it's better to go with online exchanges as when you get verified there you can use them for as long as you need them, if they exist.
