They're much easier to cook. Pour hot water in and wait a few min and that's it. If you were to make pasta, sauce, toppings, meat etc. individually using only boiling water, it'd take quite a while and probably not taste very good. But I guess if the power's out and you're not working or anything, time isn't really an issue?

Shrug. Just tradeoffs between cost, time, health, convenience, and taste, like most food.