Why should I bother with the basic drills and not just go straight to combat drills ?

I can give you many merits of doing basics drills but I argue that there are none.
One may choose to do push ups. OR  work to understand sinking within the contact and moving myself instead of pushing another and hence myself as well.
 One may choose to do sit ups. OR work to keep my alignment free and dynamic to avoid injuries and regain my freedom of movement.
 One may choose to roll. OR teach myself to keep my eyesight active all the time and to avoid clinging to a position that might get me punctured.
 One may choose to do breath training and holds. OR work on keeping my awareness and state of mind no matter what is happening.

There are no basic drills. There are no higher drills. There is only perspective and the choices that come with it.
Being good at combat drills means that you are good at performing the drills. Nature and the occasional land mine do not care about your striking power or looks. What does affect the outcome are your choices and how you keep making them no matter how your situation ventures from your perceived level of comfort .

For Philipp.