It seems like a lot of weekend warriors buy a half ton truck and then think, "Okay, I can put at least a half ton in it." Which sometimes you can and some times you can't.
I grab loads of gravel a few times a year. Dry gravel is around 2500 lbs/yard. My old 2002 F150 was configured in such a way that with me and gear, 500-600lbs was about it for the bed without going over rated capacity. I did put a half yard of gravel in it occasionally and you could see the sucker sag, but nowhere near bottoming out. My current F150 will take 3/4 ton (I think 1800lbs), so with me and gear, over a half ton easily in the bed. It sags a little bit with a half yard of gravel, but not much. My old F250 would take a full yard (I think it was rated for 2800lbs) in the bed and I could barely see the bed sag.
The loader operators at the gravel yard I use always used to ask, "Are you sure" about the full yard in the F250. Some of them have asked about the 1/2 yard in the other trucks (rightly so in the old F150).
Tires are another big deal. So many trucks these days come with lightweight passenger tires for CAFE standards that it's ridiculous.