[alehyze]

My 1) is a reply to why I did it. I took it as a literal question and I gave a genuine answer.

EDIT: Ok, I think I see what you mean now. I believe your question is about what is the appeal in doing this stuff. It's pretty much the same reason why someone would build a chair or a table from scratch versus buying one at IKEA and building it. The former gets the enjoyment from all of the journey from a piece of wood to the finished chair and from building exactly the chair that they want and the latter is probably more focused on the chair itself. END_OF_EDIT

As for the rest, I believe that some answers are already in the post and in the comments that I and other people made.

I may have misunderstood what you meant and if that is the case let's restart from scratch:

Do you want to program a raspberry pi at the hardware register level, without any APIs ?