Renter psychology

[Dominika M]

Hi all,
Newbie question: since there seem to be many areas in the US where houses cost $20-100,000 and there are several government financing programs that let people put down very little as downpayment (less than 10%), why do so many people rent rather than just buy?
I'm from the Toronto area in Canada. Toronto has average house/condo price of $550,000 and many people can't afford to buy at those prices. I honestly don't understand the psychology of the masses of renters in US. The reason I go out on a limb with such a naive question is because not understanding the psychology is seriously holding me back from investing.
There are obviously people who have various life problems (criminality, poor credit, poor life skills) who might not have it together to buy a house. But most of BP landlords don't want to rent to those people anyway.
There are some who need to frequently relocate and can't settle down. But there are millions of family people with the American Dream of owning a home who rent. Why?
I probably have some wrong preconceptions and a world view limited by my own experience. Go easy on me and share your view point.
Thanks,