First...that's a BIG assumption on your part that those with a $250K DP rig is the one doing this. That's a very rude remark.
As a park volunteer for many seasons, we saw similar happenings often and it's more likely younger folks who don't know how to manage their money that do this. They pulled in with normal family rigs. It happened quite a few times that they would actually brag about doing this practice to the rangers. They laughed about it. It is most inconsiderate to others. They are only thinking of themselves and are not thinking of how many people are being turned away by their selfish actions.
If you can't plan ahead for your definite times then go to campgrounds that are not all reservable and take your chances. Years ago no one made reservations and it seemed to work out o.k. We were never left without a place to stay.