I paddle on whitewater rivers and out in the salt water, so I have a variety of reasons for why I paddle:
-Adventure/Thrill, and a Risk/Reward balance
-Independence & Freedom from the trappings of society (affordable recreation and quality time)
-Going/Experiencing new places and meeting new people
-Maitaining a connection/relationship with the natural world
Saltwater paddling in particular has an extra appeal toward freedom: Just load the thing up and paddle off, and you are totally self sufficiant! No shuttles to run like on the river.
Most of my whitewater paddling is with other folks, for obvious safety reasons, though I sometimes run the occasional familiar class V run solo. Most of my saltwater paddling is solo unless I'm gone for more than an overnight or two.
I have one sea kayak, and 5 different types of whitewater kayak.