Well duh, @YARNLADY. The whole idea is that you believe you are unlikeable as yourself. Your only alternative is to pretend to be someone likeable. That has it’s problems, since eventually you realize they don’t like you, but some image of you that you have created. But for a while, people who do it get off on being liked. It’s a novel thing for them.
For some, it is so enjoyable, they can’t stop, even when they do realize that it really isn’t them. They reach an existential crisis about it.
You are lucky. I’d have to say you’ve always liked yourself if you have no idea why someone would pretend to be someone else. You are very fortunate. Many other people are nobodies. That’s how they feel. They feel like no one could like them as they are. They get desperate and they try to act in a way someone else would like, and when it works, they get hooked.
They are trapped then, with two personalities. One, the real them, that no one likes. The other, the fake them, that has friends and lovers. It is horrible when they are pretending to be someone of the opposite sex, because then they can never meet their lover. They get all kinds of love online, but it can’t become real. Very sad.
I don’t think you can imagine it if you never felt like nothing. Or worse than nothing. It is only real desperation that motivates people to play at being someone else. It can also happen from danger, too. Like Jerzy Kozinski’s novel, “The Painted Bird,” which is supposedly pretty autobiographical.