Packaging Guidelines: Why so lax for BuildRoot?

[Stephen Warren]

I'm curious why the packaging guidelines aren't more specific re: the
requirements for the BuildRoot tag.

To my mind, the BuildRoot is a purely internal "implementation detail"
of the build process, and no package should really depend on any
specific detail of the BuildRoot value/location.

So, I'm wondering:

1) Why doesn't Fedora specify a single BuildRoot value that all packages
"MUST" use (and possibly script an update of all existing .spec files).

2) Going further, why not remove BuildRoot from all .spec files, and
simply cause the "defined correct" value to be used without "manual"
intervention.

It seems one/both of the above would make reviewing easier; one less
thing to check (or only a single precise thing to check for, without
interpretation of what a "sane" BuildRoot is)

I feel I must be missing something given the flexibility allowed by the
guidelines. Any insight appreciated.