There is a legal one too. When Executor of the estate applies for Probate, all assets must be declared. Debts that were owed by the deceased will have to be declared and dealt with before Probate will be granted.
If the family home was jointly owned by two spouses, and spouse A leaves his share of the house to spouse B, that can only happen if the bank agree to it. Technically the bank is the owner of the home. They will have the deeds to it locked away in some vault some where. They will not be transferred to the "owners" until their mortgage is paid off. If Spouse B is willing and able to make the mortgage payments on their own, the bank will probably be ok with that. If they are not, then the bank could force the sale of the house to get their money back. Whether or not the bank would actually do so these days is anyone's guess.