Well, guess you've just been unlucky.
Have been a gold member (now diamond) due to the status match they ran earlier this year. Enjoyed the free breakfast at each property (Garden Inn, Double Tree and Hilton were the best regarding breakfast) and got upgraded at least half of the time I stayed in the Hilton Chain acorss the entire US Eastcoast, from Key West to Portland, Maine (and then inland to several other sites). Either a higher floor or a preferable view (beachview, Niagara Fallsview). Even got a suite once. This all in a 30-day period (it was probably off-season though).

There are indeed some properties that have diamond parking as an amenity, which I really like (now that I've gotten diamond status).