Yup, though as a counter, police academies really focus on the ability to generate PC (probable cause). It’s a highly prized skill.
Something hanging from a mirror, a broken tail light, out of spec window tint, child seat improperly secured, load improperly secured, weaving in the lane, driving too slow for conditions, too fast for conditions, driving inconsistent speeds, not properly signaling, failure to maintain your vehicle in a safe condition (bald tires), illegally modified emissions controls (exhausts), using a cell phone while driving, etc.
Also, speedometers are notoriously out of calibration, and no one is going to believe the driver when they say they were going x speed without some evidence.
The vehicle code is huge, and it’s a rare driver that can’t be pulled over for something. ‘Fishing’ is a common activity that catches a lot of drug smuggling, people on warrants, DUI, etc.
Speed traps also generate a lot of revenue for many departments, depending on state laws.
If you look like you keep your nose clean, you’ll usually get left alone though, unless they’re bored.
I’ve personally had at least 2 instances where I was driving on rural highways at night, and was followed for 15+ minutes by police trying to find a reason to pull me over so they could search me though. They both let me go after it was obvious I wasn’t a drug smuggler or DUI.