I think there are a couple of clear reasons why some people insist on the caravanning being emptied. When it goes to a dealers or workshop premises for service, they wont want to take responsibility for personal items that either go, or allegedley go missing. Further to that, when doing damp tests, people often store bedding under beds and that makes things more difficult for the engineer. Same for under some bedboxes where there are very often water or electrical fitments which may need to be accessed. Personally I would sooner the engineer spend time servicing my caravan than shifting items around to get access.