Sure they should. It depends on the tools available and the culture of the organization.
You don't get to dictate what features of email people should or shouldn't use.
Apple's Mail.app has a great feature that allows inline markup of images, which is a huge boon for interface discussions and tech support emails at my company.
They shouldn't but they do. Almost every time someone sends me an image I think of a better place they could have put it. Attached to the ticket in our ticketing system, in our bug database, on our file server, etc