Memes

They're becoming a lot more common. A lot of police departments didn't or don't allow them. Attitudes are changing fairly quickly, but there are a lot of old-timer gun people (including some who write policy for police departments) who see red dot sights as a gimmick, the same way weapon mounted lasers were in the 80s and 90s, or as a crutch to compensate for poor training.

They do have a couple of legit drawbacks like the possibility of the battery dying or the slim chance some part of the electronics might eventually break under force of the action cycling. And that's why you'll usually see guns with red dot optics having backup iron sights that co-witness with their dot. Also, a lot of pistol optics are open emitter designs which means, for people like cops who open carry, the optic is exposed to the weather and can collect rain, snow, or debris on the glass or between the glass and the emitter.

More and more departments are beginning to allow them though. Despite their drawbacks it's like having a cheat code for aiming. With traditional iron sights your eyes can either focus on your target or on your front sight, but not both. With red dot sights, you put the window on the target and put the dot where you want the bullet to go. You get to see your sight and your target in focus at the same time, and it's easier to keep both eyes open while you're shooting. So as these optics become more proven and "battle tested," more departments are starting to feel like the benefits outweigh the drawbacks.