My father built a Glen-L travel trailer as a retirement project. It was used regularly for about 10 years. He and my mother were the proverbial "snowbirds"... winters in Florida and Nova Scotia among other locations in New England in the summer.
When my mother passed away, the trailer never moved for the next 25+ years. When we had to move dad out of the house the trailer finally rolled when we had to find a new home for the TT. During that time dad meticulously maintain it including insurance and registration.
Even though he never used it, I think it was something for him to hold onto and perhaps reminisce. Keeping it alive even though never used was perhaps sort of a hobby.
There might be reasons beyond the obvious as to why folks do not used their RV's.