The "why" has to do with some keyboard designs that placed
a delete key more or less where backspace is on most PC keyboards.
(Examples that comes to mind are the keyboards on the SPARCs we used for
OS hacking last spring.)
As for dealing with it, there's pretty exhaustive information in
the "Delete and Backspace" section of the keyboard and console howto.
http://metalab.unc.edu/LDP/HOWTO/Keyboard-and-Console-HOWTO.html
Matt