I think that's not the only reason, sometimes not a reason at all.

Instead, 1, sometimes, someone is looking to make a career, or get a job, make money. And then, in identity politics, they might see an opportunity. Career, status, money then being a goal, and any division a side effect.

And, 2, I'm not saying that identity politics is or would always be bad or anything like that. So many unfairness in the world, to try to correct.