I have never purchased any protection from dealers. I wash (weekly) and wax (monthly) and clay bar (every six months) then wax my vehicles and they look showroom quality. To this day when I have my Vette out people ask me if it's new or hey is that a 2010/2011 etc year car because it looks so new. The Vette is 10yrs old but it's taken care of. The truck is new to me and it's much bigger and more of a pain but I will do the same treatment and the results will be the same.
I have to agree. With the paint process that manufactures use today you should need nothing more than to keep it washed and give it a wax every six months or so. To be totally honest, if you do the wash my hand use a combination of wash/wax cleaner and your done. Or even the spray wax at the local car wash will keep a protection layer of shine in place.
Dealers have been pushing the same aftermarket interior/exterior protection products for years. Why do they do it, because it is a very high profit margin product.
Now if they come out with a aftermarket exterior protection that is strong enough to door dings, scratches and scrapes it would be a different story.