The home screen does not rotate

Screen orientation is a mixed bag on Windows Phone 7. There are applications which change between portrait and landscape view depending on how you hold the device while others keep stuck in portrait mode regardless of how you maltreat the gravity sensor. For example, the mail hub rotates, contacts don't, pictures in the picture hub rotate, the picture hub itself doesn't, calendar rotates, the Zune hub doesn't, settings rotate, marketplace doesn't. See a pattern?

In case you fail to, welcome to the club. The only explanation I can think of is that Microsoft decided to have function follow form while crafting some of the Phone 7 experiences. The layout of these applications seems to have been designed specifically for portrait mode, following the premises of a "taller than wider" approach. Switching to landscape mode would imply said applications to split vertically onto two different screen, thus introducing the need to scroll vertically.

However, there is not reason for the home screen to refuse rotation between portrait and landscape mode. Currently the home screen offers space for a matrix of 4 rows times 2 columns of tiles. Tiles can be either square and occupy one tile space or elongated and span a complete row, i.e. two columns. Given this layout you cannot come up with any configuration in portrait mode that would not have a direct correspondence in landscape mode. To move from portrait to landscape would just require tiles to rotate by chunks of 2x2. I'll provide some examples to illustrate.

This is a typical home screen in portrait mode:

Rotating this to landscape orientation is an easy task. You only have to commit rotation in chunks of 2x2 tiles, just like this:

You can't conceive any configuration of tiles in portrait mode that would disallow to apply this 2x2 rotation scheme. In landscape mode on the other hand, certain configurations of square and elongated tiles pose a problem for rotation. Consider this layout, where rotation to portrait mode is not straightforward:

A very simple solution comes to mind immediately. Microsoft could simply prohibit home screen reorderings in landscape mode or automatically switch back to portrait mode whenever the user attempts to reorder tiles.

Hence the question arises: with landscape mode being a rather prominent screen orientation for many people, especially for those with heavy use of internet, games or texting applications, why does Microsoft not allow the home screen to embrace landscape?