Went to a camping in the Laurentians in Québec (Ste-Agathe) and there were those things near some camp sites. The sites are only accessible by footpaths. No car access. And if you bring a bike, you have to walk it up a hill, so I doubt they are bike racks.
EDIT: I have sent an email to the park and they have been kind enough to reply. It's just a type of fireplace with a grate. They didn't give more info than just this. Thanks to everyone for pitching in!
My guess is either a seat, something left over from an eagle scout project, or a cooling rack. Somewhere to put your hot pans/utensils to let them cool/serve from without putting them straight on the forest floor.
Like a lot of things in camping though, it's probably whatever you make of it. Improvise and have fun.