Well the bank can't get your future earnings or other assets if you default, but they can get the house. So if the house is worth zero dollars (never true) then you are 5 to 1 leveraged.
There are numerous real-life scenarios where a house is worth zero dollars.
This is not always true. (Trivially: your land is declared a superfund site. Less trivially: fire sale.)
> there are never situations where the value of the house is worth zero
I guess a decade and a half is all it takes to forget.
This varies jurisdiction to jurisdiction. And it isn't really germane to the question of quantifying one's leverage, which is a going-concern analysis.
But then don't we need to get into evaluating future earnings?
Yes, many flow leverage ratios look at this, e.g. interest to Ebit.
This is why mortgage lenders test your debt burden and interest cost against income.