Why do women get mad at us for checking them out?

I was at the grocery store and there was this chick with her hair down to her butt, wearing a yoga pants and a tight top, and her T and A were on point. I honestly couldn’t help but stare at her as I walked by. (And a ton of other guys were checking her out, not just me) she gave me a look of disgust and I was wondering what just happened? Why do women get upset at us for checking them out?