It can also have other uses. So for example if you want to use one basic email address for each member of your family, you could set up a gmail account with your last name like firstname.lastname@example.org and then assign each member of your family an email like this email@example.com for your son, firstname.lastname@example.org for your daughter, and email@example.com for your wife. Then all of you could use the one gmail account and you could monitor the family emails much easier.
Another trick is to setup filters within gmail and have your custom emails filter into their own folders. That way it will be easier to keep emails from a certain companies or family members separate from each other.
There are all kinds of things you can do with this. So get creative.