> scientists have estimated the animals consume between 5 to 10 percent of their body weight (about 40 kilos) in fruit each day

That's equivalent to a 60 kilo human eating 3 to 6 kg of food every day.

Plausible hypothesis - the chimps have developed a taste for alcohol mostly because of its higher calorie density - 7 calories/g. Vs. 4 cal/g for sugars and starches.