I'd rather just have a system that actually works. I don't care about the implementation details as long as I don't have to deal with the implementation details.
By not choosing Debian has more then tripled the amount of workload they have to deal with to make the system function properly. This not only increases their workload, it exponentially increases the amount of bugs a person is likely to run into. It makes it harder to write software for the system because now you have at least 3 different operating systems personalities you have to deal with.
Throwing scripts at it to try to automate the creation of other scripts for upstart and sysinv just means that now instead of just supporting 3 different init systems they have to support 3 different init systems and a bunch of new scripts.
To put it another way:
* It makes the workload they have to deal with much higher. This is Debian's developers problem. Maybe they prefer to play around with init systems rather then having a working OS. I can't fault them for how they want to spend their time, but... if their goal is to have a stable working OS with lots of software and third party support it's not something that is going to help them any meaningful respect in that regard.
* It increases the burden of third parties writing and maintaining services much harder. This is something that anybody trying to use or support Debian is now forced to deal with.
* It exponentially increases the amounts of bugs any person is likely to run into with Debian init's system. This is something that will bite end users and will likely contribute to issues for people that try to use Debian in production.
This is why it's a bad decision. It makes the OS worse, not better. Maintaining different kernels is very silly also if your goal is to have anything other then a toy OS, but at least the non-linux-kernel-debian folks can be marginalized by the fact that nobody actually uses that stuff. Unlike KFreeBSD I expect that they will have users that actually expect that sysvinit, systemd and/or upstart works.
And what is the benefit? So I can compare init systems side by side? Doesn't seem like much of a return of on investment.