Conversely, why bother with the making or buying the M60 when you can turn off the screen of the M 240 and ignore it when you don't need it
For me, this is not the point of the camera design nor the implications to usability that one should consider.
The bulk of cameras today have a big screen on one side and a lens or a lens mount on the other side. The screen is usually surrounded with several tiny buttons and some buttons, wheels and switches are scattered here and there wherever some free space was found. The Leica M Edition 60, on the other hand, deviates from this screen-centric digital camera design. This is a digital camera design where traditional photographic controls are prioritized and simplified. It does not actually appear all that revolutionary as it looks like a hybrid between a film Leica and a digital Leica (which very much resembles a film Leica anyway). But I don't think the idea was to be revolutionary anyway; the idea was simply to go back to a purely capture-centric approach to photography which has been replaced for many users by a capture-and-review type of approach. (No need to argue merits of either, it's not the point.)
Leica have chosen to put a large ISO wheel on the back, a very traditional choice but one that is also very practical to many users. It can be argued that ISO setting is not a similar exposure parameter as shutter speed and aperture. Rightly so. However, people often use it as such, and this is probably another way digital photography has affected camera use. I certainly like the direct availability of the ISO setting, and it is a feature that is in most of my photography more fundamental than a screen that takes a whole lot of real estate on most cameras. I would use the ISO control, I don't really need the screen in most of my photography.
While the LCD screen on the Leica M8 is pretty much useless for many review needs, it is actually quite a manageable size for not compromising the design too much. The M8 design in this sense is however flawed, it offers no ISO control outside of the menu. Today, it would probably be difficult to introduce a camera the size of the M8 with a tiny little screen on the back, even if it was top-specced. I would however like it.
Note that Leica also makes the T system (well, a camera and a couple of lenses), which is a very screen-centric design. Actually more so than pretty much any competition. The iPhone, which is often called the most popular camera out there, is an example of taking that design approach to extremes. While I like the traditional approach, I also find it very interesting what is happening in this part of the market. The Leica T was for that reason one of the most interesting product launches in digital cameras in the past couple of years.