That’s the real benefit of Airdrop. It’s so nice when you’re traveling to be able to share photos with someone you just met without worrying about WiFi hotspots, mobile data plans or any of that. You can be out in the middle of the ocean and it just works.
1. local IP network, if available
2. ad hoc WiFi, if possible
3. the Bluetooth connection
4. fallback via Apple's servers (newest iOS only)
It's primary advantage is its ability to negotiate over a number of different interfaces and protocols, as needed.
AirDrop is fast (actual transfer happens over WiFi) and easy - makes it so you don’t need to know anything about Bluetooth to use it. It’s a challenge to find an alternative app with the same level of functionality.
The requirement for network infrastructure can be worked around by creating an ad-hoc wifi network.
Unfortunately for 95% of people that you want want to share files with, that’s a total dealbreaker.