Android File Transfer not working

I have a Samsung Galaxy SIII. I can connect it to my computer via a USB cable. Android File Transfer then opens. It lets me transfer files onto the device, but drag-and-dropping files from the device to the computer has no effect whatsoever. What is going on? And is there a way to make the computer treat the device as a USB pen drive as I did with my older android device?

Update: Airdroid works. For photos, connecting as camera and using Image Capture (on Mac OSX 10.7.5) also works. USB mass storage enabler requires rooting. Still, why does that Android File Transfer not work????