Why? Autopilot used for flight controls is vastly different than for the landing gear. Have you ever flown a transcontinental flight without an autopilot? You only put the gear up once each flight but make millions of small control inputs.
So my questions why add another system that adds weight, can malfunction etc when it does not serve to increase safety or lower pilot work load. Plus what on earth would I do - talk on the radio all day? Pulling the gear for those glorious captains is the highlight of my day (yes I'm being sarcastic).