Chlorine remains on your skin if you don't - and causes constant irritation. Also if you care about hair, you should wash it out with shampoo - water alone won't remove the chlorine entirely
Not necessarily to be clean, but you should rinse off the chlorine (especially if you have hair). The hair gets really stiff & bleached if you don't, especially if you go outside in the sun for awhile afterwards, and you'll smell like chlorine.
Yes. Once in a while is probably fine - growing up I'd occasionally "shower" in the swimming pool if we didn't have power after a storm (on well water, no power means no water) - but one summer I was in the swimming pool so much that the chlorine turned my hair green.
I love swimming, and going to the local swimming pool is one of my fave things to do. The chlorine makes my skin itchy and overall isn't too good for you, so I always make sure to shower after I'm finished! There's also just an extra layer of cleanliness that is felt after using the showers
I've never been in a pool as I have easy access to beaches (I still don't go anyways). I suspect many people here take showers after going to beach, to rid themselves of the sand that gets everywhere.