Different CPUs perform subtly different. Not to mention that server-class workloads tend to expose bugs and architectural shortfalls. Ryzen hasn't had great press in this regard, so decision makers are going to regard AMD with some skepticism to begin with. It's about risk: you know Intel chips roughly perform as they always have, just a little better each generation.

Additionally, if you rely on Intel's compiler to get more performance out of your chips, well, switching to AMD doesn't make a whole lot of sense.

AMD needs to be back in the server space for a while before they'll be trusted again.