The interior of the bread pan is usually coated in some sort of nonstick, so you can't really aggressively scrub it without ruining that coating. There's a drive shaft that sticks up through the bottom of the pan, and then the mixer paddle goes on that drive shaft, so there's some bits in there that are a bit hard to clean. Not saying it is impossible, but it isn't as straightforward as cleaning a pot/pan.

Just as a note, this is the bread machine that I've got.