Because if you desperately need cash, you can trade in the $80,000 luxury suv for a $20,000 subcompact, and use that cash to pay rent and for food. It's a depreciating asset and sometimes a money sink, sure, but if you live somewhere you need a car anyway, some people choose the more expensive ones.
That's... Financially irresponsible. You build your cushion in non-depreciating assets. If you are approaching situation where you would desperately need cash, you prepare for in some way different from buying luxurious suvs.