Kayaks have overtaken Canoes because they are way more fun, they are faster (which is fun), and they are more maneuverable (also a fun thing). It's like choosing between a fighter plane and a cargo plane.
Team work is fine and all, but most kinds of kayaking are a more personal and accessible form of water sport. Being single seat and light weight by nature, there is nothing better if you want to get out there and have some fun but don't want to count on a bunch of buddies to show up with the right gear. Just slinging a craft you wear over your shoulder and hitting it is as good as it gets. (Besides, having to time your paddle strokes with someone else is why they're called divorce makers/friendship busters.
)
"Sure Kayaks are short & maneuverable, requiring less effort & cooperation, and one person can carry a kayak."
--and therein lies the point, my man!
(*If you have the choice between strapping yourself into a fighter jet and hauling yourself into a freight aircraft who the heck picks the freight aircraft?!)
I think there is something to the materials development thing, too. Canoes took off when there was a surplus of moldable grade aluminum after WWII (all that scrap B-29 material). Only makes sense that advances in materials advanced the possibilities for everyone (like fiberglass then plastic for kayak).
Good topic, though, jjdebird.