Haha, i could think of 1 reason. Erection. lulz!! Feel kinda weird if walking around with my stick "waking up".

P.S
For me, i hv a fragile skin. Havent find out whats the problem is. My skin would turn tomato red immediately with a soft slap on it >.< Even when i use my palm slap on the door softly, u can see the effect right away. So i guess im wearing clothes to protect my lovely unique skin.