I visit rest stops at night when traveling and so far never had a problem going from my vehicle to the restroom but I would never stay overnight at a rest stop as I've heard of people getting murdered when sleeping overnight at a rest stop.
Or someone tried to rob them while sleeping in a camper or there car.
Most rest stops are pretty isolated and don't have much security so it makes them an easy target for people to rob you or murder you.
I carry a gun in a holster on me whenever I travel and so far I never had to use it but it's there in case but still I would never stay overnight and find a well lit parking lot such as Walmart or Homedepot to be safer or park at an RV park.