I suspect most people use AirDrop for the use case where a bunch of folks are physically somewhere together, perhaps on a trip or having coffee, and someone asks: "hey, can you quickly send me that video?". Without Airdrop that isn't always feasible: 1) a WiFi network may not be available to send using other means 2) perhaps the video is very large and would eat your data 3) no cell reception at all, as is common on adventure or hiking trips