Interesting! We're really happy for it from an exhaustion view anyway :)
I think server hosts are likely to be in the demographic that doesn't want to use exhaustion themselves.
We get people on our server that come looking specifically for exhaustion servers.
I've considered turning it off myself though as it's just not mature enough to really use. So that may be another reason for the low adoption rate.
The biggest issue is that there is no filter and for some reason it didn't make it into 9.5 either ...