this is an observation that may be mostly supported by data right now, but also is not super meaningful.

WHY do houses appreciate? why do cars depreciate?

The answer is supply and demand: supply of housing is far more regulated than supply of cars - height limits and zoning are frequent reasons, but any sort of building approval process with unnecessary hurdles can increase supplier risk and cost. Most of these processes aren't set up with demand in mind. whereas if you are an automaker and want to churn out another 10000 cars, there's no laws stopping you (fuel efficiency / emissions requirements notwithstanding).

The problem with houses is that since a large portion of the population thinks they are investments, anything that would increase supply would devalue their investment, so fixing the regulations around them is a political quagmire.

I suppose cars, as machines, also have increasing maintenance costs over time. the same is true of houses, just over a much longer timescale... if houses depreciated instead of appreciated, we might see more torn down after 30-50 years rather than always repairing everything. Certainly the tradeoffs would start to look different.