It is rather quite simple. Any business has to make a profit. They will not make a profit on something that the customer will not buy.
There must be demand as many RV makers are offering more and more residential models. If the public would not buy them, they would not be offered.
Of course, residential refrigerators are not for everyone.
There are a lot of us that will not camp without electricity. My wife is one. She will camp without city water, TV, or even bathroom facilities in the trailer, but electricity is a must.
So we use and love our residential refrigerator.
