Software apps and physical appliances are very different, so your analogy is ridiculous.

When I email someone, software automatically routes it to the destination so I don't have to. Why should this not be abstracted across channels.

As for my trying to dictate how the recipient consumes incoming messages -- surely its more intelligent for each person to decide how they want to consume messages. I know some people who live in their SMS but ignore phone calls. Indeed the whole hierarchy of SMS / email / IM / phone / conference is very much in flux. Most people are probably more interested in who the sender is, not how they're sending.

But by your logic maybe I should use one app per person I talk to.