I know three other married couples, close enough that myself or my wife talks to them at least a few times a week.
Marriage #1 are two people who are playful with each other, and they point out hot people to each other. I think they have been married 15 years.
Marriage #2 are a couple who don't get along that well, the husband gets jealous if the wife even looks at another person of the male persuasion. Not sure how long they've been married, but it's not long. (Edit: my wife corrected me, the husband in this case gets upset if his wife talks to anyone semi-attractive, regardless of gender. He was apparently convinced that we had a threesome with his wife, but no.)
Marriage #3 are a couple who jokes with each other about it, "haha, I saw you looking at him/her". They get along pretty well. They've been married either 49 or 50 years.
Of course ancedote≠data, and I don't know everyone, but it seems to me the couple that gets jealous doesn't have the best time.
My gal and I will turn to each other and do a silent "goddamn" when we see an attractive person. Very refreshing having come off a couple of very jealous relationships
Are people not allowed to find others attractive after they’re married or something?
There's a general taboo against oogling. But its often a question of finesse. Doing a loud wolf-whistle at someone as she passes you is bad form, and doubly so if your wife isn't wolf-whistling with you.