I agree, I would rather feel a little cold the too hot, but not at the expense of affecting my general health.
I often carry a windproof gilet instead of a rain cape even if it looks like it might rain because it gives me room to carry a dry undervest to change into at the cafe as I sweat a lot. It depends on the ride, but I know that combination will keep the wind off me & fairly comfortable even if wet. I am sure most on here have their preferences, but it seems to me that with the number of new cyclists ( which is great )who have not grown up in the club world they might need some guidance. And yes i know there are some arse's in cycling clubs to be avoided.
Without wishing to appear nasty, I wonder if for some the lure of fancy helmet and glasses and the cost involved then prevents enough money left for basics like arm/leg warmers, tights, proper undervests etc. The fancy stuff catches the eye and makes you feel like a pro ? If thats the case have a look at what the pro's wear when not racing and you will see how wrong some people are.
Other people just don't get it and hopefully they don't ruin their knees.
Having said all that there are a lot of fit looking riders travelling out to the surrey hills on the train instead of cycling out from south London. A fair number of them seem to have little in the way of back up if something goes wrong, not just clothing but spares etc. But I suppose they have their mobile and credit card, but thats another story