Yes hawke, you raise a good point.
After the initial post, I did some more research and found one site where they performed a head to head comparison between screens from various manufacturers and goo systems paint. Overall, the Goo stuff did very well and if my memory servers me correctly, even beat out some screens.
Some people may not want to hassle of mounting a screen or are concerned about wear and tear, among other reasons.
Apparently there is a formula called Mississippi Mud which mimics the Goo paint and its a combination of 4 paints (Behr) from Home Depot. Suppose to be equivalent and much, much, cheaper (~40 bucks in total). I think I'll try it out.