I'm a middled aged woman, but I look considerably younger. I can tell you, you aren't doing anything and it doesn't matter what you're wearing it happens to me to. Even worse, they don't just stare, they approach. Nothing like being blocked in by a shopping cart as some guy tries to chat you up. For reasons I won't bore you with, I have a huge problem with my movement or passage being blocked.
You're obviously an attractive woman and honestly, I'm kinda convinced maybe some of these fella view that as their last chance to "nail a hot chick". Disgusting? Yes, but it's how a lot of them think, I know, I grew up with them. And they haven't gotten the memo that we're more than objects for their pleasure. Oh, sorry, they got the memo, they just never read it, probably too busy watching sports, scratching themselves, or whatever.