The Classic was very much of its time. Chris just hung onto it way too long.
Back in the early 2000s the striped rugby shirt was a staple among teens and young men (and even some particularly preppy girls got in on the action). Just look at this Ralph Lauren ad from 2004.
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These types of shirts were all over the place back then and worn by people of pretty much all body shapes (though back then they only used attractive people in advertisements).
I think Chris stuck with it for two reasons: 1) He associates it with a time in his life (his high school years) that he actually enjoyed and 2) His mind has been warped by cartoons, who always wear exactly the same outfit, and he thinks that's normal.