Why are 64 bit programs bigger as 32 ones

Question

Watching at download pages, there you always see (as far as I remember) that the 64 bit version of the same program is bigger than the version for 32 bit; Does anyone can explain that?

Answer 1

32-bit PCs have smaller storage.
64s have larger ones.

Answer 2

Thank you for the answers
@ivan terenkovskiy: if i got it right, the sourcecode is compiled and the parts of the program are stored into 32 or 64 bit fragments, if the system is 32 bit the fragments are more granular and therefore more efficient (for fragmenst smaller then 32 bit) when it comes to used storage for the binary.
@djthenoob: may I got your answer wrong, but it doesn't seem legit to me; May you intended memory instead of storage, but even that isn't the answer to my question.

Answer 3

Binary image of a program comprised of binary words. Binary word is 32 bits for 32 bit programs and twice as large for 64 bit ones.