As I understand it, the reason Leica never incorporated autofocus into their M cameras is due to the M camera ethos. Part of that ethos is that the M camera will retain the physical dimensions of the original M camera footprint. At present, there is precious little room to cram more stuff into the M camera dimensions, and an autofocus mechanism takes up a lot more space than is available in the M camera.
The M240 was .20 of an inch thicker than the traditional M camera and M camera users raised 99 kinds of hell. Leica took the hint and returned to the original M camera size specs in the M10. That involved using a smaller battery in the M10 which had a significantly shorter power life before needing to be recharged than the M240 battery, but it was a sacrifice that the gents in Wetzlar were willing to make and M10 buyers were willing to live with.
As far as missing shots due to the absence of autofocus in M cameras, anticipating the decisive moment goes a long way in circumventing that. Autofocus is a two edged sword. It helps in some situations, but is next to useless in low light shooting. AF also struggles with low contrast and subjects with little to no texture. At the end of the day, it's a tradeoff.
Personally speaking, I am actually glad my M-P 240 is manual focus. The number of images I miss in low light shooting is drastically reduced thanks to manual focusing.
