Advantages of waxing?

After hauling my boat of the lake where it was moored since June, I found a lot of scuzz caked on below the waterline. I scrubbed it off with ammonia and water and one of those kitchen scrubby things (except I couldn't get to the part of the hull resting on the trailer bunks or the centerboard, which will have to wait until I can careen the boat next summer).
I have read about people waxing their hulls. Is there a practical reason for doing this, or is it just a cosmetic means of having a shinier boat? Does the wax prevent the slime from building up, or make it easier to remove? Is there a recommended brand? Can I apply it easily while careening the boat at the beach on the lake without worrying about polluting the water?
I have read about people waxing their hulls. Is there a practical reason for doing this, or is it just a cosmetic means of having a shinier boat? Does the wax prevent the slime from building up, or make it easier to remove? Is there a recommended brand? Can I apply it easily while careening the boat at the beach on the lake without worrying about polluting the water?