Other than being incompetent to do the work, the reason people don't get hired or promoted is due to their people skills.  According to 100 top executives I interviewed the top five causes of career stagnation are:

1. Failing to expect acceptance from anyone. Regardless of rank, if you expect it you just might get it. If you don't, you definitely won't.

2. Hunch and scrunch. People who look like "winners" get hired. Winners stand straight and smile - even when they don't feel like it.

3. Being too fast. Speed in speaking, moving, gesturing, and walking looks nervous and scared. Scared people get passed over, not promoted.

4. "Tell" instead of "ask". You get hired by the questions you ask more so then the answers you give. No one likes a talkative "know-it-all".

5. Failing to showcase contributions. You can self-promote with self-respect. If you wait to be "discovered" you'll wait forever.

One of my clients protested the importance of these skills proclaiming, 'I just want my work to speak for itself'. Whereupon the boss leaned over and whispered to me, 'Then it better speak louder'.  You have to be good at your job but you also need to impact people in an effective way.