Joined: Jul 2002
Posts: 40,863
Likes: 3,115
From: Sacramento, California, USA
Bikes: Specialized Tarmac, Canyon Exceed, Specialized Transition, Ellsworth Roots, Ridley Excalibur
A lot of it is lack of bike handling skills. Because most triathlon bike legs are no-draft time trials, there's no incentive to learn how to handle a bike in a peleton. Plus, they wear funny sleeveless skinsuits.
I say this as a recovering triathlete. I still do a tri or 2 a year, but I'm a roadie now.