The problem with "
sucking what they can" is actually quite simple: When a
router or
switch is
saturated with
traffic, packets are
lost. When
packet loss
increases beyond a certain
percentage on
TCP/IP network, performance for
everyone goes way down hill. It is much
better to cap
everyone's pipe at a lower (but still
reasonable) data rate so that packet loss does not ocurr.
If all connections were TCP/IP, packet loss would not be that big a problem; since a lot of people are using streaming protocols that use UDP these days, though, routers can become saturated very easily.