Explain why the best programmers do not always make the best software managers?

Best programmers never make BEST software, for couple of reasons:

1. They think as geeks and other people might have problems to use their software (niceness are added not by programers but by completely different kind of people like management, designers, sales -oriented people). Lack of interface but good functionality is a sign of good programmers work :)

2. Good programmers know, that there is more bugs somewhere in their code and they cant honestly sell it as the best... Management and sales people do not know that their software is not the best one.