From a UK perspective, being able to cook achieves:
a) The ability to buy raw ingredients in bulk
b) You can cook dishes that last you multiple meals (and NO, this does not mean eating the same thing)
c) You can make soups and stocks from bones (all you need is bones, cheap vegetables, cheap spicing, and water)
d) VAT on raw ingredients is either 0% or 5%
e) Raw ingredients are cheaper than processed food
f) Raw ingredients are A MILLION times cheaper than restaurant prices (depending where you eat, you're typically paying up to 300% mark-up on ingredients because the restaurant needs to cover its costs)
And no it is not time consuming, the more practice you get, the quicker it becomes. And things like soups and stocks you don't even have to watch the pot, you just put it on and forget about it for a few hours.