Reasons why a home can't be moved by: On Level Services
I've never heard of a mobile home not being able to be moved. Maybe what they meant is that homes built prior to 1976 can't be moved and reused as a home somewhere else. They have to be "decommissioned". Because they were not built to HUD standards. They must be either destroyed/scraped or be used somewhere else only as a storage unit. The other reason might just be that there is some structural or safety reason it can't be moved, possibly it's structure was modified or has degraded to point that it's just not possible or feasible. In which case it must simply be demolished on site.