Why must the US Defense Secretary be a civilian?

[Happy_Lendervedder]

@Airman Doors

A person on Active Duty cannot run for office. The military has already established the proscription in that regard. So, while an Active Duty military person could conceivably become President, it could only happen through a massive write-in campaign as they cannot campaign and would never win the nomination of either party as a result.

In other words, it’s as likely to happen as Mickey Mouse winning the election, i.e. impossible. So what’s the sense in having a rule that limits something that’s already impossible?

Yeah, but the SecDef has to have been out of the military for 10 years. We’ve had more than a couple presidents go basically straight from the service to the presidency. My question is: if it’s so important for the SecDef to be *that * separated from his/her military service, why isn’t it just as important for the president?