I have discussed this with other members at Sysnative somewhat, and there would be reasons why Microsoft may not do this. However, especially if this was an app store version, otherwise would an update add it to the list of the first few already existing (non-useful) desktop apps in the minimal suite they already gave? If so, I think it would be a waste of time and effort.
Look at it from this perspective: How much time do you really spend on the desktop in something like the Surface RT, to actually justify having it there? The toast notifications would be no different than the Mail app that already exists, only, when clicked, or touched, it would open the desktop app, which would be very hard to use, because the Surface RT doesn't provide you (officially) with the pen support like the Pro version does.
edit: And by what I have read it seems like a Desktop application... :shame2: However, if Microsoft already made it though I don't see why they should not give it out. And if they did, why can't they just allow 3rd party developers to create desktop apps for Windows RT as well? To me it doesn't make sense at this point in time. I have a funny suspicion that this is because they want developers to be developing for the Windows Store instead though.
For the amount of space that they give you on RT, I honestly think that it should be optional anyways. I would never use it on my Surface RT. Why? When I already have the Mail app?