Dale Carnegie wrote a great book and yet people still struggle to influence people, here are my thoughts on why...
1) Say one thing do another
2) Say of course I won't tell anyone......
3) Manage up not manage down
4) Desire to be nice not constructively honest
5) Treat people how they want to be treated instead of how the individual wants to be treated
6) Stay in their office, rather than be visible
7) Respect their own views more than other views
8) Believe that once you have left college you have stopped learning
9) Settle for what they have rather than living their dream
10) Seek approval rather than the right answer