Families in that income bracket can usually afford a home without assistance. Because families who make less money -- and who often struggle to keep up with house loan payments -- don’t pay more in interest than the standard deduction, they don't even claim a separate deduction for interest, and thus get no help from a tax break supposedly intended to help them realize the American Dream of becoming a property speculator.
In sum, as presently structured, the deduction gives the most help to people who don't need it so they can buy more house than most of them use. A better idea is to simply let people deduct a percentage of their interest as a credit against taxes owed. That way the owners of modest houses get the same break as the owners of mini-mansions. Until this or similar reforms are adopted, the MID will remain bad law, bad policy and bad finance – which, I guess, explains why it has so many supporters.