I think the peeresses were probably glad of the warmth of their robes at the last Coronation, which happened on a cold and rainy June day. It's not as if the Coronation is a ball; it has its own dress code.
I also think that if anything a Coronation of Charles will be as elaborate as he can make it, and that there is a good chance Camilla will be crowned. If she were not, where would that leave Catherine in the next reign? I suspect there will be as much adherence to tradition as possible. William, on the other hand, might streamline traditions while still following them.