Because the net meter (DU Meter) that I have sitting at the bottom of my screen constantly displays how much bandwidth I'm using. It seldom exceeds 2mbps except for file downloads (and some web pages). I keep it there to check how much bandwidth I'm using for specific tasks (downloads, streaming video, VoIP, etc.). Video streams typically approach 2mbps (peak) before filling the buffer.
And having a 30/5 connection makes it very easy to determine how much of it I don't need for some task.
