
To begin with, female lions (or "lionesses" to those who enjoy stumbling through words that end in too many S's) do the majority of the hunting, most likely due to the fact that they yearn to be in charge and feel important. Because female lions spend so much of their time hunting as a result of their pride (or "for their pride" as it's generally stated), the responsibility to babysit falls on the unfortunate males.
Now, babysitting is never easy, but imagine doing it full time while you're also trying to get twenty hours of sleep a day. That's how much an adult, male lion sleeps. You may not know this, but you can't really get much done when you're only awake for four hours a day. I did it for about six years in college, and even if someone had been doing all my hunting for me, by the time I'd eaten dinner and watched Monday Night Football, there's no way I would have been up for babysitting. Male lions are getting robbed! And on top of that, sometimes they're raised by sheep.