If you were to describe a group of poor illegal immigrants who live in tents under a bridge, would you say that they are "camping" under a bridge, or that they are "camped" under a bridge?
If I write "Homeless man camping under a bridge" (e.g. in a photo caption) might it perhaps sound like he is camping there for fun? Does "camping" sound like it's a leisure activity, and "camped" (as a past participle) like it's a makeshift form of accommodation for the homeless?