but there's something about the Watson himself (other than the direct influence of the Holmes) that prevents him from being the perfectly socialized specimen that he at first glance seems to be.

Book!Canon Watson admits that he is of 'a Bohemian mind', considering himself an writer/artist first, doctor/soldier/husband second. His life with Holmes is considered an exercise in classic Bohemianism, at least to Watson. His attachment to Holmes is partly due to his rejection of rigid male roles, making him queerly delicious.

IMHO, they are basically a pair of Victorian hipsters. ;)