Why do ATM's keep card sometimes?

Question

Even non-branch ATM's that do not return your card. Why does this happen?

I recently had to wait till my bank open and had a employee fish it out. Kept it for no reason same thing happened with wells fargo so its not just one bank or ATM.

Update:

Tonight I was at a gas station and the ATM kept someones card so this reminded me of this issue. Kind of crazy seems like a big problem if this is common.  

Answer 1

The return mechanical mechanism didn't work. 

Answer 2

If you don't pull it out within a period of time, the ATM will "eat" it.  It's so that if you left it by mistake, some else can't take it.

Answer 3

cause they like your card, i dont bother with the atm , i just use a debit card

Answer 4

They do that when they are expired or have been reported missing, that's the only time I've heard of it happening. Other than that it's a fault.