You act as if it's impossible to overdress. Getting your attire just right when you don't know how the weather will be is very difficult (especially as it can be a lot of different things on one ride). If you overdress and sweat on a climb, you can easily be worse off on the next descent. Plus this isn't a club ride with coffee breaks --- apparel may have gotten "better" over the years but it hasn't gotten easier to put on or take off in the middle of a race, quite the opposite.
5C is no problem at all if it's dry and sunny. Water is way more of an issue. So I don't see that statistic as particularly meaningful.
In the particular case of FW I would blame the team staff for not paying closer attention to the weather forecasts which may change suddenly, as they sit comfortably in the team cars.
I agree with some of what you said but not the bold:.
- First, look at the forecast. It can't be that wrong few hours before the race. It just can't.
- It is a fine line between being overdress and not. There is just no excuse with today's gear. Just not. I do it all the time and people laugh at me and call be jungle boy. You can take your vest, arm warmers off in a hurry. Even the gloves. It is very easy. It is harder to go back to the car to request it and put all that on. The Shoe protectors, can be aerodynamic and does not compromise being warm. Not at all. These are just excuses by the riders. And excuses for nothing with todays technology. Look at the winner and the way he was dressed. If it was going to be sunny I am sure he would have tossed the jacket, gloves and arm warmers to the side of the road in a hurry. No more than 30 seconds. And no waste of energy. This is just riders being silly like Chris Horner said.
- No excuse for the low fat climbers being this underdressed. Just no excuse at all. Please don't play the macho man thing.
- Last but not least, sometimes the sun is out but it is just painted. It just makes for a beautiful picture because it was freaking cold with the Windchill factor. The guy who makes the videos at Movistar came out of the bus with long sweat pants and a thick hoodie and the first thing he said while filming was, "Sh!t I wasn't expecting to be this cold with this beautiful sun". Then he looked at his backpack for an extra jacket. And that was only with the sun out. Don't get me wrong but the macho culture and testosterone sometimes can get to you. I go for a ride and everyone looks around to see who everyone is dressed. The sun is out and most everyone start taking the arm warmers, leg warmers, and gloves off. Then everyone does it and look for who to bully. Look at the riders when they were signing to register for the race. They were cold, red faces, and all bundled up. Then they all showed up half naked for the race. Go figure.
- Last but not least, look at some of the big guys who had extra fat. they were bundled up. The irony!