Because programmes like
check_soa from the O'Reilly book "DNS and BIND" or
believe it makes sense to force a dot at the end of
every name they look up.
There are nameservers in the root zone file that DNS will
not find. /etc/hosts is the only way to get them.
Dont forget to have both names with and without dot.
That is horrible, but I have to live with it
Peter and Karin Dambier