A decade or so ago, while living in the Philippines, I noticed that serving sizes were much smaller than in the USA. I recall approx. 8 and 12 oz beverage cups being quite common. Filipinos would laugh at how one of the first culture shock moments they experienced upon visiting the USA was the enormous soda pop cups that they would be given at fast food restaurants.
Why do we have such huge plates of food and huge bottomless mugs of beverages at restaurants in the USA? I think it's because food is cheaper than labor here.
The Philippines has a high rate of population growth; its primary product seems to be its people, who go abroad as maids, nurses, teachers, seafarers, nannies, and manual laborers to the US, UK, and Middle East. Security guards and salespeople abound at commercial establishments. While one can sometimes feel at a US store that it's impossible to find an employee, in the Philippines we were once nearly mobbed by around ten salespeople anxious to sell us bedsheets in which we had expressed some interest.
When labor is relatively cheap, employers can more easily dip into their margins to hire more employees to attract customers with better service. But when food is inexpensive compared to labor costs--such as where there is high minimum pay and employment taxes--restaurant operators can more easily offer generous serving portions to try to entice customers.
I know I'm not an economist, but this article made me think that my idea is not silly. They're going to automate parts of McDonald's food production at a new restaurant in the Midwest but still hire many employees, and a new attraction will be "all-you-can-eat fries." That doesn't sound necessary or healthy to me. However, while potatoes, salt, and oil aren't free, they probably cost a lot less than new kiosks and employees whose minimum wage is likely to go up in the near future. Without customers, there's no way to pay labor and automation costs, so increasing food amounts beyond that offered by the competition is a logical way to try to stay afloat financially.
I like fries, I really do. But I also like not feeling guilty after eating an extra large serving of them. I'm OK with small portions of oil-drenched starches.