It depends of when your devices were built.
AirDrop works differently on Macs from before 2012 -- AirDrop used Bonjour and personal area networking (PAN) to discover and transfer files between Macs. When AirDrop came to iOS 7 in 2013, it used Bluetooth LE and peer-to-peer Wi-Fi to transfer data. It was an incredibly secure implementation, but it wasn't compatible with the older version present on the Mac. MacOS now supports both versions of AirDrop — the Bluetooth LE/Wi-Fi protocol and the Bonjour/PAN combo — but it defaults to the former.
Can you please post your Mac and iPhone specific models?