I know that you are supposed to travel in business attire to be first choice for first class... I lean on the I want to be comfortable when I travel side but that's just me.
For our recent trip I decided to try and look cute instead of rocking Pj's... thought this was a bit more appropriate. Rocked out my thrifted necklace and vest and was on my way.
I also tend towards being cold on planes... why? I don't know you should ask the airlines why they like it feeling like an icebox! ;P