Because you own a piece of property whose value (you believe, arguendo) is going to plummet precipitously sometime in the near future. Now I don't know if (under our hypothetical) you're still paying mortgage payments, but if you are, once the bubble bursts you're still going to be paying off the home's pre-bubble value. That's... bad. (Note also you'll still be paying property taxes based on the pre-bubble value, at least unless/until reassessed.) But even if you've got the house all paid off, it makes sense to sell simply from a profit angle.
Now, I understand you like your house and don't want to move. Simple: find a buyer who just wants rental property, and sell on the condition that you can continue living & renting there. You'll probably have to sell below current market value, of course, but what's wrong with that? The bubble's gonna burst! And then after the bubble bursts, of course, you can always buy back your home for half its current value (or whatever) and pocket the difference.
(Note: there may be some form of home-equity loan which is essentially equivalent to doing all of this, I'm simply not informed enough to know. But if so, that's the way to go.)
If you truly believe in this "bubble" stuff, you'd be foolhardy not to do something like this. You may as well just throw money away.
Aw this ole bubble ain't gonna burst ;)