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.
If it had no top, the poles could damage the tarp, or it would be a pain to tuck it in around it.