Maybe think about it this way. For many, a camera bag is nothing more than a device to move somewhat delicate equipment from one place to another AND NOTHING ELSE. IOW, once you get to where you're taking pictures, the bag isn't very useful. Example - You take a pic of the Mayor on Main Street, put your camera back in the bag, walk 20 feet, pull your camera out of the bag, take a shot of a window display at the Emporium, put your camera back in the bag. Oh, wait, Marie is actually out, gets the kids, pose them, take your camera out of the bag, take a shot, and put your camera back in the bag.
See? So if your bag isn't for the camera, you gotta ask yourself whether anything else you bring through the turnstile is really going to make a park experience that much better compared to the incovenience the weight the stuff represents. Unless you are going with multiple bodies and lenses, bags in the park can be worthless from a camera viewpoint. Maybe there's an argument for a belt-type toploader but that's questionable. Of course, this doesn't stop scads of people from bringing as many of their worldly possessions as possible into the parks but that's between them and their comfort and sanity.
I too happen to be in the multi-bag club. Huge fan anything by LowePro's with the AW designator, especially in Florida weather. Then again, I've learned that hanging anything more than 15-20 ounces off my shoulder on a long September day in Orlando is a no-win situation. It's a lesson once learned that sticks with you.