It’s true … but besides that there is more likely to be an epic than a legendary, most of the legendary are class 2, or those that you can get from epics.
And another thing … it takes away emotion that is a single item per box. When you have 2 or more items you are more excited to buy. But when you only get 1, you disappoint. It’s a basic marketing concept, people are curious, they like to guess, to see things. It becomes more entertaining and encourages to buy when there are more items.