Is the entire length of a credit/debit card used?

So, it occurs to me, that only a third to a half of credit cards seem to actually be used when you do something like insert it into an ATM. I'm not sure about how much space and physical car you need for swiping though. I suppose my question is: are credit and debit cards the size that they are because it's... show more So, it occurs to me, that only a third to a half of credit cards seem to actually be used when you do something like insert it into an ATM. I'm not sure about how much space and physical car you need for swiping though. I suppose my question is: are credit and debit cards the size that they are because it's actually needed for them to work, or are they that way for convenience AKA fits in your wallet perfectly and is more comfortable in your hand. Like, could a credit or debit card potentially be the size of one of those membership keychains that you can get at places like CVS? And would they work just as well?
4 answers 4