The world is full of curbs, stairs, lips, rugs, vehicles, etc. If you're a human-scale robot then your wheels need really wide base to not tip over all the time, so you are extremely awkward in any kind of moderately constrained space. I wouldn't exchange my legs for wheels. Wheelchair users have to fight all the time for oversights to be corrected. I can see maybe see a wheel-based humanoid robot, but only as a compromise.

On the other hand there is not much reason to constrain ourselves to the unstable and tricky bipedal platform or insist on having a really top-heavy human-like torso. You could have 3-4 little legs on a dog scale body with several extra long upwards reaching arms for eg.