Though the article on untucked shirts is a bit dated, regrettably the fashion statement of untucked shirts remains current...
http://www.nytimes.com/2004/07/20/fashion/20DRES.html?ex=1248062400&en=395983a3aacfd28f&ei=5090&partner=rssuserland
It certainly was true for me in the early 1970s. what greater statement of rebellion could one make?
Well, youthful styles like untucked shirts can look fantastic, if they are on a person of the right fitness & beauty, and it's the right kind of shirt. That's really the essence of a lot of the bumbling with style and clothes in the general public: people just naturally assume that things are either 'in style' or 'out of style', and if something is 'in style' then it will naturally look good on them, even if they are potbellied with Elvis sideburns.