It also depends on how popular the place is, and the customer demographic. Continuing with that example, if it's a small grocery store in a town with a population of a few thousand people, sure, there's definitely no point in having 24 different types of jam. However, if it's a store specializing in jam, in a large city, then having a larger selection makes sense, especially when you have someone working there who you can ask to recommend something. Sadly that usually also implies higher prices.