Chocolate has been consumed for at least 2000 years--but it wasn't sweetened at first. People realized the food, or drink, did seem to add energy to their body. Yet it was an acquired taste and beyond the scope of most.
One of the first recorded comments concerning chocolate refers to it as suitable for pigs. This may not have been a reference to the fact that pigs are lowly animals, but because sows can be quite unparticular about their diet.
If you've ever tasted cocoa powder straight, you can understand this. The bitter taste will convince you that a sweetener is needed. Sugar wasn't as plentiful in earlier times. Cacao seeds needed to be roasted and ground. Pre-industrialization this wasn't as simple as it is today. It's easy to see why chocolate wasn't a food for the masses.
With the advent of steam power, desserts had a chance to change.
The first European chocolate drinks were spiced and made with water. Some people included port or brandy with their beverage--but only the more affluent could afford to indulge at first. With the price of chocolate and sugar both reduced and more readily available, it would be only a matter of time until consumption grew.
As of 2014, Switzerland consumed the highest amount of chocolate per capita according to The Chocolate League tables. That's not so surprising. But the USA ranked 17th which made me realize my neighbors might not have the same dietary habits I have.