If he cares about her, he would know to let her go earlier on so she doesn't get more attached and like him more. This way by not spending a lot of extra time before he cuts her out of his life and he becomes an important character in her life, it'll less the pain of splitting up rather than having her grow even more found of him. He'll let her go though, because he doesn't even care about her so why would he waste a lot of his time with someone he doesn't care about?
If you think about it, this relates back to
Can't Remember to Forget You
with Rihanna. In that song, Shakira talks about a relationship that's
not working out. She knows he's no good for her but she still has
feelings for him, and won't break things off. Here's where we get
You Don't Care About Me from. Shak's been putting all the effort into the relationship and it's not working out, like in
CRTFY.
Since Shakira "keeps forgetting she should let him go", he decides to
terminate the relationship, and here in this song are the results of
that.