Why not use me?

This is not to say I want to be used because I don't. I want to be valued and loved and respected. But I do wonder why would he not have wanted to use me anymore?

He left and got an older woman, he'd said to me that he doesn't think he'd be good for me and that he should find an older woman, his age. He did within days and he did send me some personal texts while with her but then was rude to me and ignored me. So why did he choose to just ignore me then? Why did he choose to leave in the first place when he could have kept using me?