I actually did remove the rubsigns from some of my Transformers when I was ickle. It was because of the concept of proving they were genuine Transformers. My logic was, I knew that they were proper Transformers, so why did I need the rubsigns? So I took them off. Off the top of my head, I know Optimus is now missing his rubsign. I think Thrust, Bumblebee, Warpath, Cosmos and Powerglide are missing theirs. I'm not sure who's missing them altogether.
I really liked rubsigns when I was little. I think it's a neat little gimmick. Doesn't make much sense, but it's an extra piece of fun. Plus it proves that you have body-heat and aren't some sort of cold blooded VAMPIRE
Rubsigns were useless in hot weather because they revealed a Transformers allegiance without the need to rub him up! Punch/Counterpunch hated hot weather because whenever he was trying to infiltrate Decepticon HQ the heaters in there revealed his true allegiance!