Is it fair for Infantry Branch or Engineer Branch to weigh so heavy on tabs for promotion to Senior NCO ranks.

I feel that those are two of the greatest leadership schools that you can attend but is that what really makes you a better leader? Like someone in my case I can not pass the physical because of blood results and I have Rheumatoid arthritis. Now possibly that could stall my career. Just because someone has it the "Board" could pick someone over a more fit leader because they have it. Through out my time in the Infantry I have met tab "Wears" and tab "Bearers" just because they have it doesnt make them more fit to lead a Company. You will always have good leaders that dont have it and bad leaders that do have one.