If a Starfleet cadet turns tail and runs, would they ever get command? "Risk is their business", according to Kirk. If a cadet doesn't want to risk, they shouldn't be in Starfleet, much less in command of a starship.
One ship against an enemy fleet. All that will be accomplished is the death of your crew and the destruction of your ship. It doesn't seem to be bravery and sacrifice, it looks more like suicide.
"Yeah, we'll give you a command. We love commanders who get themselves and their crews killed by going into a no-win scenario ignoring the escape option when the only other option is death."