Seriously, building in general in blockland is ultra-abusive. That is why admins are important in servers. Just because people have a new way to build does not mean the admins are unable to clear their bricks and ban them. Events are much more abusive than BuildBot.
Events are easily regulated. And yeah, building can be abusive when users are enabled to use it in such a way that clicking a button takes full advantage of its abusive potential. From the standpoint of dedicated servers, admins aren't always online. It's not so much a matter of admins being lazy, but just another problem they'll now have to look out for.
If someone made a script that allowed clients to, say, rapidly fire a weapon, would you decry its abuse factor as a consequence of projectiles? And rapidfire scripts can be prevented with robust weapon scripting; buildbot is a different matter entirely. And while it's true that rapidfire scripts can be useful while building or copying events, it's even more true that rapidfire scripts are more often (and easily so) abused in DMs and such. Thus, its abusive potential outweighs the benefit and you have something that is wholly abusive.
You could even go as far as to say that the duplicator is abusive, but that can not only be regulated but is limited by trust. Once again, buildbot goes further than this.
My point here is that releasing something this abusive to the general community has nasty drawbacks. If, like the redo add-on, this were server-sided, there would be no issues with abuse.