Ha, I think that argument is made by people who don't have kids (with homework). It's not leisure for me at all. While I worry about being branded a terrible father for this comment, I will admit that I am a terrible teacher. I have no patience for it.
My kids mess around, constantly want breaks ("Well I've written a line! time for a 10 minute break!"), waste hours doing shit that should take them minutes... When they start "accidentally" dropping their pencils on the floor because they'd rather be faffing around picking it up than working, I often just lose my temper. Man, I'm getting slightly pissed off just thinking about it now! xD
There are brief moments of joy/relief where you can see they've grasped a concept or improved and you can be proud of 'em. But most of the time it is a frustrating experience, slow going, and a slog to get them to do anything. The worst of learning, with the worst of kids messing around, with a massive feeling of wasting everone's time.