In every ATM I've seen, the card is "swallowed" by the machine, and returned at one point or another (or not, if you type the wrong PIN 3 times or whatever). This leads to people forgetting the card, as exemplified in Why don't ATMs give you cash before your card?
However, many other machines - vending machines, auto-parking, gas pumps, supermarket auto-checkouts, etc. - only require that you swipe the card. This looks better to me - the card never leaves your hand, and you're much less likely to forget it.
Why this difference between ATMs and other machines? Is it just so the ATM can swallow your card if it doesn't like you or your PIN attempts?