That happens. People also have stocks that go up 1400% in 2 months. Its just not something that a betting man would want to place a wager on. The average person doesn't make a lot of money on a house over the course of 30 years.

Mortgage interest is tax deductible but its still a bad deal (you're still paying 3/4 of it, just getting 1/4 returned). It doesn't nullify the overall cost of home ownership though, even if you bought the house outright it'd be a lot smarter to take that $300k or whatever and leave it in a balanced fixed income portfolio.