User blog comment:Sannse/Welcome to Community Central/@comment-5175866-20160623173842/@comment-8-20160625135601

Many of the tools just need one place to reside, especially those that have a global effect. Central is just an easy place to keep them.

The main tool that I can think of that is per-wiki is checkuser. That is set up to be on each wiki, and to just give results for that wiki.