Sup /out/,

I recently went for a tour along the Federal Highway from Sydney to Canberra (Australia) i rode the whole length along the shoulder and everyone was great, trucks gave clearance when i was going over bridges and the motorists didn't honk and try to distract you as do some towards cyclists, i did, however get lots of horns and waves from Motorcyclists passing by, is this a friendly gesture passing by? Why is it that it was only motorcyclists doing this, and not motorists, just curious. Also, what are your experiences with motorists/motorcycles whilst touring?