Why do lions hunt in packs? Because it is more effective. I guess you already knew the answer. The females do most of the hunting while the males do the fighting. When the lionesses set off for a hunt at dusk and find prey they approach with great caution while the group fans out sideways to encircle the prey. At that stage they are working together.
When individual lionesses are close enough to their target prey they attack reaching speeds of up to 40 miles per hour (64 kilometres an hour). The prey becomes confused when faced with attacks coming from different directions. Individual prey animals may pause not knowing in which direction to escape, which gives a lioness the opportunity to reach the targeted animal and knock it over with her forepaw. The lioness pounces on the fallen prey and suffocates it with a classic throat bite. It is held until the animal has passed, and for longer sometimes.
We can see that by hunting in packs the females achieve a better kill rate but the challenge is demanding and only about one in four hunts produces a result (20%-25%). In other words the mighty lion loved for its courage and stature but hated for its brutal killing of beautiful animals fails 75% of the time when hunting.
The diminutive black-footed cat is more successful. Their success rate is 60%. This makes them up to three times more successful than lions. The black-footed cat is a harder worker than the lion. In one night a single individual can kill between 10 and 14 rodents or small birds. This averages a kill every 50 minutes. The lion sleeps for 16 hours out of 24!
Sources: PoC via Wild Cats Of The World (the Sunquists) and Cat World (Dr Desmond Morris).