Why Do Men Find it Acceptable to Walk Around Topless but Women Aren't

I was at the lake today and I saw tons of men walking around topless. Mainly older men with not so great shape but it still makes me mad they can do that. They would rather have their shirts off. Even at pools it is okay for men to go topless but not women. Even in some public places like the store, I have seen men walking around with no shirt. I feel like women should be able to do that too. This likely isn't the best place to express my opinion. I feel like it's not fair that it is okay for men to go topless and women can't.