I think the big difference for me is that for many airlines, hotels, and even rental cars, you accumulate miles/points/etc by either consuming the actual airline/hotel/rental product or by some other means (an associated credit card, shopping through a portal, partner offers, etc). You are also able to spend those miles/points/etc either on future travel plans or sometimes other products.

It looks like the two frequent parking companies that have now been mentioned in this thread seem to have one way to earn rewards (by using their parking lot frequently), and one way to spend such rewards (free/discounted/more convenient parking). Neither has a credit card associated with it, and neither allows you to redeem your "rewards" for anything that I could find other than parking-related services.

There doesn't seem to be quite the level of complication with frequent parking companies that there does with the frequent flyer/stayer/renter programs, and trust me, I wish that all programs were as simple as the parking companies seem to make it! ^ But because it is so simple, it just doesn't seem to me to warrant a complete forum for it, especially since, as mentioned before, there probably aren't a lot of people that would frequently use parking services at more than one airport.

Perhaps you could answer the questions in JDiver's post, which might give the Talkboard a better chance at understanding the need for such a forum.