This is a compliment! I am 35 and still check out a handsome 20+ male. I won't do it blatantly but with discretion. If he is handsome, smells good or looks dynamite I will probably look. Regardless of our age, if we find a man attractive, why not enjoy the view? :)
I have seen and experienced with men too. Funny, these men are in their 40s and 60s too.
Why do older man look at younger girls? Simply women glance because they like what they see, doesn't mean it's only because of the age - if you look great and feel great than you definitely will get attention, from everyone =]
This is because you're hot and if you were interested in them it would make them feel very confident in their ability to capture your attention especially since time has ravaged their once youthful looks.. so its a compliment for you to glance back despite the fact that the women your own age would be considered more attractive, its all about competition. Just because she is in her late 40's doesn't mean she isn't a woman anymore... if you catch my drift ;)