Comment 5 for bug 1585589

It's not so much about maintaining upstart as it is about maintaining upstart support in every daemon, and making sure the boot sequence continues to function well, etc. That's completely wasted effort, and the only reason we made sure it continued functioning up until Xenial was to make sure that upgrades could run smoothly.

Putting alternate init systems in universe without also committing to support them would be naive at best, actively harmful to users, at worst.