It would be interesting to analyze a dataset of commercially sold prepared "coffee" drinks from vendors like Starbucks to see how many are actually coffee, versus coffee-flavored soft drinks, and how this changed over the last few decades.
It's hard to work around the fact that coffee, dairy, and sugar taste really good together. Coffee really wants to be a dessert, it's why it's in so many of them. Starbucks just rolled with that and people love it.