Why do people that drink coffee, keep drinking coffee after the 3rd cup?

At my “day job” I see a ton of guys drinking coffee throughout the day.  Not Starbucks or McDonald’s coffee, but just regular torke coffee made in a regular coffee maker.  Now, I don’t like the taste of regular coffee and will only get one kind of Starbucks coffee.  But what I think is weird, is the fact that they are drinking coffee throughout the day.

Does this actually keep you awake or “stimulated” so they say?  I just can’t imagine that after the 3rd cup, you might think to yourself, “self, why am I still drinking coffee to ’stay awake’?”

Since I don’t drink coffee, I just thought I would throw this one out there to the masses to see what sort of replies we get.