Initially, this approach had many advantages, because every team could individually configure its Jenkins instance and toolchain without being at risk to break

Initially, this approach had many advantages, because every team could individually configure its Jenkins instance and toolchain without being at risk to break each other's pipeline. This was just fine. After some while, when CI is running well, the focus goes away from CI to other fancy development things. So, updating and maintaining the CI pipeline becomes a more dull job and we think about replacing the individual CI pipelines by a unified one.