If my house value falls, broadly speaking, other ones fall. If my house value raises, broadly speaking, other ones raise.

Buying a house means, generally speaking, I can kinda "guarantee" I can afford that "quality" of house. It's like having a housing share that I can exchange for another similar house.

If your home value increases, because regional home values increased, you also can't move!

That's only relevant if you intend on moving someplace else. Most people I know who own homes have no intent of ever vacating them.

Many(most?) people do not plan on ever moving.

why not? if my home value falls, presumably the one I'm going to move into fell as well.