Here is a tid-bit of trivia for everyone on the subject! Did you know that up until 1955, saddles were only made to fit the rider, and not the horse? Very little consideration was given to a horses back on the show circuit. Perhaps that is why around the 80's no saddle pads were used, because at that point, saddles were being manufactured for the horses fit. And like someone said before, as saddles get more and more expensive, you want to preserve the leather... And to increase the number of fun and colorful appearal you have for your horse, of course!!
"There is something about the outside of a horse that is good for the inside of man." ~ Sir Winston Churchill