In any category, light buyers (i.e., those who only buy the category occasionally) favor large brands over small ones. This is known as the “Natural Monopoly Law” (i.e., larger brands monopolize light buyers) in How Brands Grow.
This is because light buyers are less aware of the different options in that category, and they will just “default” to buying the brands that immediately come to mind–in any category, these will be the large brands, because they can spend a lot on advertising, and Marketing must build availability.
The inverse of this law is also true: because light buyers favor large brands, you must target light buyers if you want to grow (Brand growth comes from light buyers).