Why not disembark crew after deploying WW?

[Schastny]

Is there any reason not to disembark the crew after a war wagon is deployed? Doesn't the decision to keep the crew embarked limit its ability to rotate and shoot with a full arc of fire, without offering any advantages in return?

[VideogameghisKhan]

If you disembark the crew, do they lose immunity to being pushed back and consequently losing the fortified spot? (Or does being behind fortifications make a unit immune to pushback already? Some game concepts are hard to find the complete rules for.)

[rbodleyscott]

If you disembark the crew, do they lose immunity to being pushed back and consequently losing the fortified spot?

Yes