Airdroid uses a lot of bandwidth that I'm not so sure Bluetooth can handle.
Sorry, but I don't think this is accurate. I am tethering right now over bluetooth and I was able to get 2Gb/s d/l and similar u/l on speedtest.net on a "mere" 3G connection. Maybe bluetooth cannot manage connections as fast as the latest WiFi versions (I don't know, maybe it can, for surely bluetooth is also being improved?), but a 2Gb/s connection for example is fast enough for most operations.
I am strongly in favour of AirDroid adding BT connectivity, because it has some major advantages:
1. Bluetooth consumes much less energy than WiFi and mobile data
2. Reliability: If your laptop is paired to your phone, you can
reliably initiate the connection
straight from your laptop. I know this is possible with a wireless hotspot, but if you have this on all the time, your phone is likely to have ran out of batteries before you even try to connect. So then there is the phone's internet connection. This will either be via WiFi or the phone network (assuming you have a data plan), but let's face it, this can be unstable, e.g. no WiFi and no mobile data signal, or in the case of my phone, it is unable to work out the WiFi doesn't work or requires login (I know newer Android versions can figure this out and automatically switch to mobile data). So, you must take out your phone to turn on the wireless hotspot or figure out why you can't connect over the internet, and for me this sort of defies the purpose of AirDroid: If I have the phone in my hand I might as well do what I wanted to do straight on the phone.
1 is the big one, but I think 2 has merit also.