Though it is easy to blame the borrower
And it is true they are to blame for a lot of the problems. We also have to blame the mortgage companies that are in cahoots with the realestate agents that decieve the borrower/buyers into thinking they can afford the house.
The companies that through pure greed don't even hold the mortgage lone enough for the new buyer to move in before it is sold again and again. Then let's talk about the insurance companies that see you have just had a recent increase in debts so your credit score drops then they double your homeowner's premiums hence increasing your escrow requirement and forcing the people to pony up up to 75% of their income.
There is an old saying in lending (I used to be a loan officer and collector) "If you aren't helping someone, you are hurting them. It is the lender's responsibility to steer the buyer into the best product for them. If they can't afford it, deny the loan.