“So That’s what Bivouac means” achievement does not count if you have a camp skin equipped. It’s a hidden achievement so my guess is that most players either finished it while leveling ages ago or they assume it’s way more difficult to complete than they expect and don’t bother.
I had it 66% complete for ages and finally found an achievement list with a description of how to complete it. Only after removing my camping skin was it possible to make progress.