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.
This is to make sure your carry on fits on the trail (jk)
Is the area prone to bears? Could be the remnants of a small bear box for a cooler or something that went over it, either some sort of information kiosk or storage/waste box that’s no longer there.