No doubt some fat and lazy people appreciate coffee delivery, but I think probably a lot of slim, highly motivated and productive people do as well. (Also, surely, a few serial killers and pedophiles.)
Adequate human interaction (modulo the ongoing pandemic) is indeed important (I think, at least for most people), but a wide swath of people probably have an overabundance of it, and wouldn't benefit from the additional interactions involved with physically going get their own coffee from some human in a coffee-vending establishment.
The positive use for drone delivery is the same for any other delivery service. The pros and cons compared to human delivery, animal delivery, wheeled robot delivery, etc. are debatable.