[xaduha]

You have a good analogy attempt there, but you didn't quite nail it I think, because Outlook is also an email client.

It's more like if someone asked why they need to choose between [e-mail] address or [e-mail], but in reality email would work just fine regardless.

EDIT: fixed

[tedunangst]

Except for all the people with outlook.com addresses.

[arjvik]

Yup, you're right. I guess I was specifically referring to outlook.com, Microsoft's hosted email solution for consumers.