If you want to leave something for your offspring, make it a priority to pay your house off first.
It's not like they confiscate the whole house because you still owe $100,000 on a $250,000 home. But the survivors do have to keep the home out of foreclosure (as in, keeping the payments current)
I can't tell you how often someone's heirs either didn't know or didn't care enough to take care of what was required to keep the mortgage in good standing to sell the property and get the equity out.
I'm not trying to judge what you do or what situations you're a part of, but it doesn't sound much different than the "vultures on the court house steps" to me.
But doesn't non-secured dept result in the same thing?
I mean if I can't pay off the credit for a degree or car or boat, won't they come for my house too?