I'm sure a lot of guys do that. But my impression (and I knew him pretty well) was that he did it out of insecurity. He tried to make himself into more than what he was. I don't think he was any more insecure than the rest of us, this was just his way of dealing with it. Like I said, he really didn't need it, girls liked him anyway.
This just goes to show what I've always thought: They supposedly respond to confidence, but they don't really know what genuine confidence looks like. You just throw up a front and that's good enough for them. This was back in our early 20s. I imagine we all had our own insecurities, but we knew we were supposed to act confident so that's what we did. I guess you could say that's a form of lying, although I see it as more as conforming to society (in this case masculine norms - those still existed back in my day).