We would like people to stop using https://wiki.jenkins.io/display/JENKINS/Maven+Project+Plugin but the user base is still growing (less quickly fortunately).
I think one of the main contributors to this is that it is actually impossible today to not install that plugin. It's pulled in by basically the whole world.
So for instance, even if it's not explicitly in the Jenkins 2 installation wizard list of plugins, it will always be installed transitively.
Then, imagine a newcomer installing Jenkins for the first time for a try, using Maven and Java on a daily basis... Installed Jenkins, clicked "New Item", who is not going to click on "Maven Job"?...
So if we ever to move forward and see the usage of this plugin decrease significantly, we need in my opinion to first work so that it is not automatically installed on every single Jenkins instance in the world...