Without the ability to identify and map your Ethernet interfaces to the correct interface name at boot time you end up with a mess that you have to go back in and fix manually.  The udev subsystem does a horrible job of mapping interfaces to anything sane.  With parallel device driver loads it assigning interfaces to names with no sane way to predict what it's going to do.  In a server environment where specific interfaces may need to be mapped to specific networks and functions the ability to identify and assign interfaces to names is extremely important.