When do we lose the ability to skip?

This afternoon I saw a young girl, I would guess a pre-teen but just under 13, skipping to her parents car. She was obviously happy and the skipping was just an expression of her joy. It was so uplifting and even though I was just driving by it made me feel good about the world.
When do we lose this? Why is it that adults do not skip? When was the last time you skipped for joy? It seems to me that boys lose it quicker than girls. Fact or bias on my part? Why do I feel as though if I skipped people would give serious consideration to putting me in an institution? Thoughts? Comments?