Tere's simply no rational reasons to run ARM servers.
Unless you want an extra security layer that consists of "something that isn't x86". The ARM architecture is much more difficult to implement some types of common x86 attacks. Some type so return oriented programming type hacks are extremely difficult. Some architectures use hardware stacks so there is no addresses of many things on the stack so they can't be accessed that way at all which is a very common x86 attack.