It is more of an economic thing than not.
For most public (USFS, State Parks, etc) campgrounds, they either do pack in/pack out for free or boondocking sites, and for public lands campgrounds that charge a camping fee, they provide dumpsters. Depending on the size of the campground, the dumpsters are located near the entrance, or perhaps there are a couple of sites scattered throughout the campground.
Many of these campgrounds used to have smaller garbage cans located throughout the campground, but these were replaced due to critter problems (bears, racoons, etc) and the fact that USFS rarely has their own employees doing garbage pickup these days. With the dumpsters, they can contract to a local garbage service that picks up once or twice a week.
The only time I could see the OP's option 3 is if you are at a highly developed RV park and want all the comforts of home. I for one, would not want to be walking through a campground and see bags of trash lined up along the road.