The presentation library is written in the internal core in C++. If you try to use it on system that do nto have it, you get “not supported” exception.
The Bitmap class is a part of a much larger system for graphics (presentation), in which doesn’t fit on a single chipset (USBizi). Systems that support bitmap (part of presentation lib), like EMX, have megabytes of RAM/FLASH.
Another thing here is the runtime RAM usage. When you write your own code, not depending on bitmap class, you can decide how to manage resources to fit your needs. The 60KB of RAM found on these small devices can do a lot of amazing things if managed properly.
Finally, not all users need graphics on those small system, actually most of them do not. It would be a bad idea for GHI add something internally that use more of the precious resources. Leaving it out, make the resources more configurable.
We work very close with many users and always try to come to the best common grounds to everyone, the ones that need graphics and the ones that do not. So, even though we didn’t include graphics internally, we still explained it in the book and gave you all source code you need to do graphics … and provided a ready to run display board too