Controlled by media, society,etc... While these things are more than likely the primary concern for most gear-less riders, some people simply do not give a shit about getting hurt even after they have been severely injured.
If we are to generalize then there is a high probability that the herd mentality is what dictates acceptability on both sides of this argument. The ATGATT guys are equally guilty. Still there is a small percentage that simply does what they feel like doing even at the expense of "coolness". In the end I will just never understand why the other side feels the need to look across that line and cast judgement on the choices of others... I guess it's just part of the social paradigm with regards to the human herd.