Way back a long time ago (before the Interstates) there were these things called "service stations" that had bathrooms. They were far closer together (in distance and time) than the "rest areas" along the interstate.
Sometimes you just can't WAIT another hour to drive the 60 miles to the next "stop". Or, to put it another way---"When you gotta go, you gotta go."
At least folks are putting the result in containers---it could be "pee against a tree". Which is worse???
The containers, for sure.
Every other animal on the planet pees right where it stands, including animals on the side of the highways. If it were that dangerous to humans, we'd all be dead.