Why do Rally cars have 4 doors?

[adamk24]

I have been curious why most rally cars are still 4 door vehicles. I cannot think of any good reason, other than ease of production, that they would be sedans.
I mean I know that alot of rally cars are hatchbacks like the focus and the golf, but why do cars like the Evo and the WRX remain sedans? If anyone could shed some light on this, it would be appreciated. Thank!