32-bit?! Seriously, Intel? Makes me think of Jaguar. 64-bit! Do the math!
Intel's engineers are smart enough to know with the target platform for that particular line of Atom CPUs, the extra die space and power needed for 64-bit is a waste. You don't need the memory addressing, you only marginally slow down memory access, and for most applications having quad 32 bit cores will be faster. (Remember, its a CPU targeted by Intel to get the low-end of the tablet market back from ARM, so its meant to be as cheap as an ARM CPU, as power thrifty and only has to be as fast as a competitive ARM CPU. And it does meet that.)
Its expensive for what you're getting, but the convenience is probably worth it for the premium, especially if you were VERY space sensitive.
That said, for about the same cost you can get a vastly more powerful MicroATX solution. It'll just take up more space.