Comment by thaumasiotes

The most popular flavors, by definition, benefit from advertising the most. The goal isn't to achieve equality of popularity between every product you sell. It's to sell the greatest number of products!

The advertising costs the same whether you advertise popular flavors or unpopular ones, but you'll get a lot more sales by advertising the popular ones.

Go check out a grocery store, see whether the aisle caps slant towards popular or unpopular product varieties.