Just to be clear, this is a real question. I'd like someone who likes and uses buildout to engage in a constructive discussion about its merits.

I don't think the Python community in general dictates the use of buildout at all. I reckon there are more supporters for pip install -r (although I would take correction). So the question becomes, why some smart people consider buildout Pythonic. I guess they just like it.

Buildout came first and can do more things than pip can. If your workflow was heavily dependent on buildout, I could see how someone would see pip as inadequate. Buildout also came from the Zope community, so that will immediately break people up into camps.

My impression is also that more people use pip now particularly with its integration with virtualenv.

I can't imagine not developing with pip and virtualenv now.