Why can't TW add friendly fire in siege but server hosters can?

[_COS_]

I just played a siege hosted by Rdc clan and it had friendly fire on siege. How is it that they are able to add friendly fire without servers crashing but TW can't? A DR hosted battle on Echerion also had no snow map but TW hasn't removed Echerion snow map for 5-6 months now.
@Callum @Dejan @NIN3

 

[Younes]

I don't think that you realize you just wrote it is possible.

 

[Mushbeast]

According to the developers it leads to more crashes, though that may have been fixed by now. The reason the server hosters can is because they quite literally just have to enable it when hosting.

 

[AoC]

Shouldn't there be friendly fire turned on official servers?