Question about peanuts

I was wondering this:
When you buy peanuts in a can it is smaller than when you crack them youself from the shells. Why is this?

I assume tou’re talking about the size of the individual kernels?

There are different varieties of peanuts, but I think I’m right in saying that they fall into two broad categories; one variety has deep red skins and up to five kernels per pod, the other has pale red/pink skins and only one or two kernels per pod; the latter variety seems to be the one most commonly sold as ‘monkey nuts’.

Oops, I neglected to mention that in the varieties with only one or two kernels per pod, the kernels tend to be much larger.