Imagine that it's already half past eight in the morning and you should have been on your way to the office. There is no time to prepare the usual coffee and have a croissant. You must hurry to the bus station. Luckily, the bus has no delay and you are now almost next to the office.

Notice that you are not really familiar with the store and its products. Scientists say that the most popular size of coffee anywhere in the world is the medium size. And it doesn't matter how much coffee there is in that medium sized cup. "Small" is just not enough and "large" is simply too much.
To Think About
Based on this idea product assortments can be optimized to maximize profits. Increasing the number of options in an assortment can encourage demand for the middle choice.
Source: Soman, D. (2013). Course: "BE101x Behavioural Economics in Action". edX platform