Since most people who buy a 1/2 ton aren't pushing them to the edge of their envelope, they never pay attention to the payload. Typically when you buy a crew cab, you sacrifice some of your payload. My buddy was surprised when on a fishing trip, I indicated we should take two vehicles. He couldn't get it through his head that between 4 200+lb guys, a 5000 lb boat and trailer combo, and all our camping and fishing gear, we were well over the payload rating of the Ram 1/2 ton pickup he wanted to take. (Payload was around 1200 lbs!) Granted it makes for an awesome ride when its not loaded, but way more people overload these trucks without realizing it...
All that being said, you typically can outfit your 1/2 ton to get a higher payload if you need it. All that being said, when its needed, I'd rather be behind the wheel of a 3/4 ton or higher...