The first thing to remember is the real purpose of a slip. A slip acts as an intermediate layer to separate your body from the dress itself, this has many advantages, it helps to smooth the overall appearance, it allows the dress to move free of the body so will hang better and look better, older dresses were designed to be worn with a slip, without, they just will not work as they should. A slip is essential under thin material as it stops the ‘see through effect’ and in cooler weather it can also act as a extra layer for warmth, plus a glimpse of a slip under a dress has a magical effect! A slip works better than a sewn in lining of a dress as it is free to move separately from the dress itself, attached linings don’t do this they move with the dress which sort of makes the lining almost a waste of time.
So to answer your question, should we all be wearing slips? My answer is most definitely!!