Houses should be investments... in the same sense that a good, durable pair of shoes is an investment.
In a well designed system, the value of property should stay pretty flat over time, and the value of a structure built on that property should slowly go down over time as wear and tear sets in.
It's ridiculous that it makes sense to buy more home than you need, and to hold onto a house longer than you need it because it's one of the best and safest money-earning investments you can make. It's especially annoying as someone in a position to make that investment gets to live inside their investment and enjoy it even as it appreciates in value.
Nothing else works that way. Can you imagine if you bought a classic car and drove it on the road as a daily driver and it went up in value? Or, if you bought a rare Magic the Gathering card, used it in your regular deck, and somehow it only became more valuable?