there are all the reasons in the world to keep drinking or indeed smoking
to quit its as simple as a desire to do it and having the will power to follow through
everything else is an excuse
The same goes for dieting to drop to single digit body fat levels.
It's a simple process. You reduce calories, lift weights, do cardio if necessary at the end, and be patient. But 99.9% of people can't do it.
In conclusion, being shredded through quitting junk food and being in a calorie deficit is harder than quitting any other vice.