I can understand your sentiments. However, I can see the other side too.
Keep in mind not everyone is using touchscreen. The majority of desktops and some laptops are in this category. The start screen in Windows 8 started out bring not very friendly with a mouse and keyboard. This made a lot of people hate the new metro interface. If you had a touchscreen, especially on a tablet, it was great. Then there is the fact that in general, people have a tendency to resist change. For the most part on my desktop I use that compacted menu. With a large monitor and high resolution, i don't have to move the mouse all over the place. I pin apps and programs I use heavily to the right side and use submenues fit the rest. This is much easier on the multitasking aspect. On my tablet the metro interface is what I always use.
As far as my desktop, I have 3 icons: computer, my user folder, and recycle bin. I like my cycling pictures as backgrounds.
I wasn't talking about using a touch screen save for noting that they mangled the touch interface as a by-product (though I have several examples of both m+kb and touch device). All I'm saying is that crunching the start screen down to a small size in the corner of the monitor, on a desktop m+kb driven PC, doesn't seem overly useful. Mainly because it is completely impossible to interact with the rest of the screen content without dismissing the start menu anyway. So why shrink the start screen down to a tiny area in the bottom left hand corner? You tell us you can see the other side, but offer little as to how making the start menu miniature is in any way useful. Touch or mouse, it seems to make little difference. The full start screen is in every way just better, as far as I can see. You do mention keeping mouse movement down on a big screen, but I suggest with a screen that big you should be using touch as mouse is not ideal for such a huge space. Still, if a small start menu is useful to avoid excessive mouse movement, why would you keep all your icons way over on the right? Surely if icons on the right are convenient as you suggest, then tiles on the right would be equally convenient?
On balance, it sounds like you need a smaller monitor (or try adjusting the scaling) as yours seems an impractical size for your purposes. Perhaps several smaller monitors and multiple desktops would be better?
One use, I suppose. If a person is using the massive Microsoft Windows Hub device with a mouse, it might take quite some effort to move across the whole start screen. A miniature start menu could be handy in that situation. However, if this shrunken menu was added purely to benefit that somewhat niche market then I'm a monkey's uncle. We think Windows Phone has a small footprint, how may MS Hub devices actually exist I wonder?