Wicks moisture away, prevents chaffing. They are probably not needed for less than 2 hour rides. I never wore them until the late 80's, but I would get a lot of chaffing sometimes. Now I never get chaffing.

Having said that,...

The expensive ones, like the ion in the voler shorts do this better than others, but when I go on centuries, the overriding comfort factor is the periodic change in shorts- not what the padding is made of.