Cops have always had tremendous discretion in what and how laws they enforce. this is not new news.
Things that affect if they pull you over:
If you look like you are screwing around while driving
If you have crap sticking out (feet, boards, etc) of your crummy looking car
If you are driving an extremely expensive car and look like you shouldn’t be the driver
If they are trying to fill an end of month ticket quota
If they have been told to generate more revenue from tickets
If it’s a slow day
If you are speeding over 10 mph posted limit
If you’re driving with lights off in rain or snow or night
If you hit the brakes while speeding after you pass them
If they can hear your music blaring before they see your car
Forgot, if you shout “I thought I smelled bacon!” when you pass by them