Why are women so sneaky?

In my personal opinion, and I'm a straight male btw. I think that women are this way almost by nature. I personally think they are sneaky/insecure because of various traits that I've noticed that many women share, for instance a form of sneakiness/being incognito to me is when women will wear shades even on a cloudy day (I never understood that), or they will look away when you are walking towards them, and then sneak a look just when you pass them (some straight men do this to men btw). An example of being insecure is... and I know plenty men can relate to this, is when a male (me) will be gazing at a decent-hot looking woman in public, and there will USUALLY be another woman, less attractive of course, giving me the eye, as if I was their man.