Rejection of fashion has always seemed like a fear of failure to me. Trying to dress well means exposing yourself to evaluation, comparison and the possibility of getting it wrong. The traditions and standards of fashion have accumulated over centuries and are fairly resistant to being redefined (especially by rookies), which makes success depend on external criteria and not on personal rules. Rejecting fashion altogether removes the risk of failure.

I think this is reflected in how techies are drawn to the safety of techwear, where fit and color matter less and clothing can be chosen and justified through objective criteria like weather resistance parameters.