Yeah, had loads of these today

Worm.Automat.AHB
Once again I have to wonder -
why has Microsoft written an email client that can be taken over in this way ? How many of us want, need or use the scripting capabilities of Outlook to send messages to people in the recipient's address book ? Is there
any legitimate non-virusy/wormy reason for wanting to do this ?
And why not just allow people to switch it off so you just have a program that sends and receives emails ? Or would that be far too sensible ?