It wasn't always that way on gmail. I have a long-lived account and someone else has in the past had a working address of the same words without the dot but always used the @googlemail.com address.

Note: my bit of research into this taught me that the googlemail.com domain is used by Gmail users in Germany, Russia, and Poland where the Gmail trademark was already taken 1. In each case, Google was forced to use “googlemail” and therefore googlemail.com instead. As of 2012, the situation with Germany was straightened out and new users to Gmail there get assigned a gmail.com domain.