The majority of working days, nominally at least, include an hour for lunch. That hour used to be spent leaving the office, finding a nice eatery somewhere nearby, and sitting down with a friend or colleague for a light meal. In the 1990s and earlier, you might even have an alcoholic drink with that meal. Try telling that to a millennial, and they'll congratulate you on your wit and repartee as soon as they've stopped laughing.
Millennials - like most workers - are finding that lunch hours are increasingly a myth. Although employers can't make it a policy, there's a quiet expectation that you'll eat a snack at your desk and carry on doing at least some work during your mealtime. Besides, snacks contain fewer calories, and aren't as expensive. The millennials are saving more money, and employers are getting more labor. It's capitalism in action.