If you own multiple homes, then you can view all but one of them as an investment, as you can sell them when the market is good.
If you own one house and have a mortgage on it, then the market going down is bad because you end up with negative equity.
If you own one house with no mortgage, then the market going up is bad because it’s harder to upgrade. I wouldn’t mind my house being only worth £10,000 if it meant that I could buy my dream house for £20,000.