Primarily because less experienced users could be doing a 40 - 60% optimal deployment today.
The thing is that you're worried about snowflake deployment. You're still in the mindset that your app deserves special treatment; if it doesn't stage and launch using community-accepted best practices, then the platform is to blame.
I disagree. If your app needs zany configurations just to launch, I think that's a smell.
From time to time on buildpacks we would receive bug reports of the form "my app doesn't work". Usually, upon closer inspection, there was an easier fix: follow best practices.
The thing to remember about PaaSes like Cloud Foundry, Heroku, OpenShift and now Otto is that they are opinionated by design. The goal is not to provide an infinite supply of knobs and dials. We tried that with mod_perl, with PHP, with Java. It's a freaking nightmare made of sentient, glutinous mud that wants to eat your soul.
Our job as engineers is not to tinker. It's to create value for users and businesses. Clinging to the illusion of control is wasteful. When I fly I don't care about how the plane works; I just care that it's fast enough, safe enough and cheap enough.