The mortgages that banks make have risks associated with them. That's why they charge an interest rate, that they themselves set. No one forces them to give out loans. Now, if the government mandated an artificially low interest rate in return for homeowners promising not to walk away from mortgages, that's be a whole other matter. The banks aren't innocent victims. When they write the mortage, they assess the risk, and choose to accept it, along with the reward.

Also, businesses do this all the time.