This. Back in high school me and a girlfriend were chilling at a park one night on the hood of my car, about to make out, nothing illegal. A cop drove by and gave us a bit of trouble, and I was pretty pissed at the time. Looking back on it though I totally understand why he had to check us out. Two kids, at night, in an empty park, not doing anything. Yeah, definitely suspicious.
If you're doing sketchy shit, you shouldn't be surprised if a cop pulls you over or checks you out.