|www.rodneybeede.com||"I would love to change the world, but they won't give me the source code" - unknown|
I was wondering why and found the following bug report that explains it. In short the password value is optional since -p alone means prompt the user for the password. Most other utilities use something like "-p -" to indicate prompt from STDIN for the password. MySQL does not.
One shouldn't pass the password on the command-line anyway. You're better off putting it in a mysql.ini and securing the file instead if you need it for automation.