Did my own informal survey this morning.
Part 1: observation - no more than one in ten females wearing UGs.
Part 2: question "How often do you wear a dress/skirt" - The responses ranged from once every two weeks to once a year or so.
Part 3: question "When to wear a dress/skirt" - Formal occasions or special events (weddings, etc).

One lady, when asked, said she couldn't remember the last time she wore a skirt -- but was wearing one at the time - lol.