It sure beats being uncomfortable or having to strip off all the paddling gear to answer the call of nature. They eliminate having to sit down in the sand to wrestle with an ankle gasket, which you'll probably just rip anyway. I wear socks inside the booties for comfort, insulation, and longer bootie life. Finding something to wear on your feet while paddling used to be a hassle. Maybe it was wet-suit booties or sandals or just an old pair of Chuck Taylors.
Today there are several shoes designed specifically for kayaking.
My favorites are the Patagonia Playboots. They are high top, flexible, and low profile, have a very good sole for wet rocks, and provide excellent support when you are portaging 60 to 70 pounds of boat and gear on your shoulder. I started out in the seventies thinking wrestling shoes were the ticket, but they fell apart too easily and had no traction. The Playboot is a climbing shoe that is at home in the water and will probably save a few folks from sprained or broken ankles. Not only would the Playboots stay on your feet in a swim, but they would also be invaluable getting back to civilization.