Majority of the food sold in the UK contain nutritional values, how much of a daily intake, how many calories, all that stuff.
Alcohol, on the other hand, doesn't contain such information. Given that beer is very frequent addition to the diet it should be clear what is getting into a body.
My theory is that nutritional value is plausible (very low) and if people knew that what inside they would think twice and the sales figures would decrease. Does it have any backing in consensual reality?