_Land_ appreciates. "Real property". Many homes are built on land, and either come with the land itself as a package deal (almost all standalone residential property is like this, in the UK it would be "Freehold") or is offered as a long lease with an inherent interest in the land (more common where multiple homes share footprint, in the UK "Leasehold" or the more modern "Commonhold").

The building doesn't appreciate, if you spend $5000 on home improvements or repairs almost invariably an honest agent will tell you the value of the building was only marginally increased by doing this, because it was never the building value that mattered.

Where people just own the building and NOT the land, "mobile homes" or "manufactured homes" depreciation destroys the value of the home relatively quickly, within a lifetime usually.

Primary reason is that property has a stable value as you said.

There is also another reason. In most jurisdictions a mortgage is a super senior claim. It is senior even to the taxman, which is very rarely the case for private debt.