The majority of properties I've rented have been directly from the owner. Yeah there's the risk of it being a scam, but you can tell (or at least I can) pretty easily when it's legit. When there's a property management company, there's an added cost, sometimes significant. Cut out the middle man and deal directly with the owner and save some money. Plus dealing with the owner directly, there's room to negotiate on arrival times, price, pets, what have you.

For example, I rented a ski chalet recently. The official check in time was 3:00pm. I told the guy, I'll take it, but on the condition that you let us check in at 9:00am since we're flying in bright and early and it would be nice to put everything inside before heading to the slopes. Owner said, sure. Stuff like that is a lot harder to do when you're dealing with "Becky" at the 1-800 reservation line.