I live in a pretty dry area. I can think of only one area with pretty dense foliage within a couple hours of home and that's in a seasonal stream.

In the winter I've often been in areas with half a mile line of sight to any place you could actually get to and plenty of canyons where anyone coming around the bend is going to see you, period.

Summer provides a bit more cover at lower elevations, but as you go higher there are trees but you can see under them and in many cases getting off the trail is difficult.

If you hike long enough trails to need to relieve yourself you know there's a small chance you'll be seen, and likewise, you know there's a small chance you'll run into someone relieving themselves--if you can't stand either scenario, don't go.