In my 12 years of insurance experience I've seen it more often than not, where the replacement cost is much higher than the mortgage. Especially when the home is older. However, I've spent most of my insurance career in Cleveland, OH, and that may be why I've seen/experienced this. It could be different in other parts of the country. For example, I currently deal with NY, but I still see more often where we have to increase the replacement cost of the policy vs where we're telling the insured they're overinsured, and that maybe the overinsurance is because they were trying to cover their mortgage. Like 4:1.
And since insurance doesn't cover the land, that's never a consideration for me (for what I do).
OH, but I was talking specifically about the replacement cost of a mobile home, not a site built home. People ALWAYS underinsure their mobile home. When I realized that this was about a trailer, I corrected what I wrote.