you don't need the bucket, and you don't need to attach the kite to the boat.
True. The bucket is for convenience. I find it much easier to avoid snags as opposed to unwrapping the lines from the bar. Trying to unwrap from the bar while the kite is drifting was difficult to stay ahead of the kite, and I had more problems with twists. It just works better for me. Of course, you can just coil the lines on the floor of the boat, but we usually have a couple of bars rigged in buckets ready to launch if we get a kite Kooked up and have to recover it in deep water.
Attaching to the boat is another convenience. Sure, I could have it hooked to my harness, but then if it is wrong, it is more difficult to deal with while it is pulling on me. Also, I have the leash hooked to the boat, so if it gets really crazy, I can just flag the kite and recover it. Again easier than having it pulling on me.
As with anything, I am sure there are multiple ways to do this. I have had good luck with this method. Definitely open to other ideas.