I get how you feel, it's kinda overused but that's what actually happens when you like someone, get jealous of whoever is lucky enough to spend time with them
I also agree that it's overused, but it's common for people to feel that way IRL. It's rooted in insecurity and jealousy. If someone doesn't feel like they're enough or they don't feel like they're important enough, they get these thoughts of "so you flash that smile at others too," or "Why do you look at them that way." They're insecure without reassurance, not understanding that there's still this awkwardness between them, especially when they haven't settled their relationship. They can't see that them not smiling around them means they're shy or they're not fully comfortable with them yet, and they're able to smile at others that way because they aren't conflicted around others.
Source: trust me bro
bruh i hate this trope of “he smiled. therefore, they make u happy and i dont. now im jealous” whole time they r actually just talking about u. like people smile all the time for different feelings and reasons!! its such a lazy way to cause drama