Hot/Cold behavior with friendships or acquaintanceships?

Let me first off say that when I'm about to ask is NOT indicative of ALL younger women, but a trend I noticed with SOME younger women I have come across. I'm not trying to make a sexist generalization, but this is just my experience.

There are certain women who are a little bit younger than me who I will try to be friends with and I will be friendly with in a non-flirty, genuine/real way. They know my intention is not to try to date them or show romantic intent but merely to be friendly.

And I get the indication from them that they are not interested in being friends or they take my company for granted, and when that happens, I walk away.

But as soon as I disappear it's almost magically they are interested in me again and they actually make an effort to talk to me, and say something like "Hey, I haven't heard from you in a while. How are you doing?"

Younger women will actually approach me and do this when normally they wouldn't do it and most of the women I dealt with are more introverted.

Why am I magically more interesting when I walk away?

Is this a game? Have I shown that I'm a more desirable or valuable male since I'm able to walk away from them?

What's up with this behavior?

Thanks!