* Was it simply a technical reason. IE we don't know how to do it?
Technical and historical. Integrating into the canon menu system would be no more or less legal than anything else CHDK does.
Much of the canon UI appears to be in structures in ROM which include function pointers. While I haven't looked into this in detail, it might be quite difficult to override this without moving too much stuff to RAM (unlike RaduP, I do not believe that you can move the entire firmware to RAM and still have it function).
The alt system is also quite simple, all you need is to hook they keyboard task and write to the bitmap buffer, so you can get it working with fairly minimal reverse engineering. This is the historical reason.
