It's more evidence of the "instant gratification" thing. Stick the box/packet/bag in the oven or microwave for 5 to 20 mins and bingo, tear into it, no prep and only packaging to dispose of and maybe some cutlery to wash. No long and tiresome prep, 2 to 3 hrs cooking, and massive washup and drying. Collapse in the sofa with insta-grub or after it and get on with real life, e.g. X Factor, Coronation St, Love Island.
The illegal drugs win out for the same reason. Drinking enough to get any kind of "buzz" takes time. Drink with benzos or other CNS depressants and you're flying sooner; take heroin, skunk, cocaine, crack and you're off to the races quicker and may still be able to "enjoy" a drink.