A robot that isn't stationary, in a home or in a factory, wants legs. Wheels are fine for cars but not great for stepping over things (like on cluttered floors) and stairs. So legs, assuming we've got the compute and algorithms to get them to work well, only make sense. The rest allows for application of creativity. As a human, have a head, my brain is in it, as are my eyes. Humanoid robot doesn't need a head, and can have cameras in its chest and on its back, and then also have its brain in the chest. Depending on what's useful, it doesn't need to be limited to two arms. It could have one centrally mounted in its chest, with two cheaper ones on both sides. Or four, two on each side. I've wished for three hands before. The problem though is that they look weird. Any non-traditional design is going to fall into the uncanny valley, so that no matter how much better your non-traditionally armed robot is technically, it's just not gonna sell to the mass market. We only have to look at weird cars/vehicles which have a history of being boondoggles. So it's not a failure of imagination, and more a matter of practicality.