Remember, it's possible for BOTH the renter and landlord to be making an optimal decision - if you rent for $1500 a month, when you could buy the house for $100k, that seems dumb but...
-What if you plan to move in a year? Or you're not sure?
-What if you hate doing home maintenance and fixing appliances?
-What if you have other (tax advantaged?) investment opportunities that you'd rather max out?
Remember, if your renter bought that house and sold it a couple years later, they'd probably walk away with nothing (or worse) after figuring in the various costs of buying and selling, unless the property appreciated a ton. Even worse, their downpayment money would have just been sitting in place instead of providing a tax break and generating dividends/capital gains.
Many renters rent because they have to. But there are many who rent because it makes sense for their lifestyle and financial goals.
-W