AlpineCadet: It is considered an option because it is the default option on vBulletin and nearly every other forum solution. On top of this, the vast majority of implementations offer this basic functionality. E-mailing is not the closest thing to private messaging, private messaging is one or two tickboxes away.
With that said, I do understand the policy, and see no reason to change it (at least for myself).
2 x [Babolat Pure Storm Limited] , MSV Focus Hex 1.23 @ TBD