Because, just like the new kid at the "cool table," he is telling tall tales to impress everyone. I've known more that a few pathological liars who never seem to learn that everyone is on to them.
There is a guy from MN that frequents AGW who tells lies to impress everyone, and they buy it. I met him once, had his number quickly. Tales of his derring-do, of wrongs committed against him, etc. Complete BS'er. Nobody has called him out yet that I know of, but I challenged him one time about one of his stories, he got a bit indignant, and expanded the lie to a story that I knew with absolute certainty was a lie. More than anything I felt pity for him, sad to need to make up such stories trying to get respect and admiration.