If a sinkhole developed, my house burned down from lightning, or an earthquake destroyed it, I'd get the insurance proceeds. There's no similar insurance my investments will stay the same or go up.
I calculate my house value minus the mortgage in my net worth because it is an asset. I don't use a strict figure for it (I recognize the market changes month to month, and it may be up or down slightly, plus I'd likely have broker fees and closing costs), but hells to the yes I'm not going to ignore the $400k+ we have in there. That's ridiculous. If we needed to, we could sell it. And once the mortgage is gone, it will reduce the income money we need in retirement. But I don't count it as income producing either, when I'm calculating how much I need in income producing assets to have 4% spin off each year, because I won't be selling off 4% of the house each year.