I think it has to do with the philosophy of the lightweight packer.
Camelbacks are systems. They have packs you place them in so you can wear them. That makes them heavy. I have seen many a hiker use their 3L Camelback full of water strapped to the outside of their pack. If you just use the bladder and place it in or on top of your pack with a hose it is still a heavy option.
Platypus are light and fold nice and small. I am like many here. I use a 1L bottle, such as a plastic WIDE mouth soda bottle that goes in a pocket on my pack. I refill as needed. The Platy stays folded up for later use. When I get to camp and I need more water, fill my soda bottle and my 1L Platy for dinner, etc.
I had one develop a small leak on the side. Patched with those little Platy patches. I am sure it was from using it around granite surfaces.
Scott

