When its teens and young adults, usually their inexperienced in life and to see a person different, or that their curious about, they hang around, to see. Sort of like spotting a unicorn, your never going to see that again. Older people in their 40's and beyond, we just go "eh", seen that, read that before. Sometimes with younger people and stalkers, you have to call the cops/authorities, to put a stop to them, because usually my experience people like that are like a pack of excited hyenas, they get more intrigued if you pay attention to them, and if you show fear, or anger, then, they really want your attention.
Used to happen to me in my 20's, now in my late 40's, nah, or I just don't care. My girlfriend does get oogled from time to time, and I have to escort/do errands with her at times.