Why is it that when you’re finally happy with someone other people start to take interest in you?

It kinda makes you wonder if they actually liked you this whole time or they decided to finally make a move because they realized you weren’t within their grasp. It’s like how most girls would go for the jerk rather than the nice guy. Why? Because it presents a challenge. It’s common for people to want something, or in this case someone, they can’t have because the struggle makes it seem like its worth it. No one wants something they can easily have because what’s worth achieving if its already in front of you? It’s pretty irritating and naive but it’s true.