So, why is it that men have such insatiable urges to give head whenever they get excited?

It's like:

"You know, I had a very good time with you this evening. We had a nice dinner and a walk in the park, and at the moment I am greatly enjoying kissing you. Allow me to eat you out as thanks." Head under skirt, mouth on vagina.

 ....WOAH, THERE. I had a good time too, but you know, this really isn't all that necessary. Whenever I get happy that a boy buys me an ice cream cone, I don't grab a penis. Is that the sort of thing expected of me? "Oh [Tyrone], thank you so much for this slice of pizza. Hold on a moment while I dust the floor before I get down on my knees."

Calm down, son.