My sail racing days led me to be stuck in thinking a kayak can not be sailed, or is not worth sailing.For many years I would not even consider putting a sail on my kayak.I outright thought it was a stupid idea. Then I discovered the truth of what a good sail can do for a kayak.
I can tell you have not used a well designed kayak sail. Do not let conventional sailing thinking fool you.If you want to sail with a perfect sail boat, you can do that and carry a sail with you when you want to paddle.
A properly designed kayak sail can be very efficient.
You can easily sail to within 60 degrees of staight up wind. That means 66% lines you choose can be taken.If you concentrate just like you have to when sailing a dedicated boat, you can do better than that.With some smart planning, you can increase your actual sailing routs to be very high.
If you demand perfection you will loose out in opportunities.I guess a typical dedicated sail boat may be able to sail 75% when everything is going great and you are concentrating.If you paddle sail, you can go closer to the wind than you can sailing a dedicated sail boat. About 30 degrees down from straight up wind. This means 5 out of 6 lines can be taken.
Use a good rig, add some tacking, and you are sailing even more. Some days we sail a 90% of the day, and could tack to make it 100%, but choose to paddle cuz some times its just faster.
I remember my days of sailing, and I would just not go becuase I would not go unless I knew there would be wind. Hanging in a sail boat without wind is the worst.
In my kayak, I go even if wind is not a guaranteed thing. When I paddle with a sail its no problem if there is no wind. I just leave the sail down and paddle. If there is wind, pop the sail up and sail. If there is light wind I paddle sail. Its a good time.
Here are some pictures of the sail down.
http://www.falconsails.com/KayakSailingFAQ.php#lower
If you are in a kayak, and the wind dies, you have a paddle ready to go as a back up. That beats the hell out of motoring in.