Python packages don't install on /usr/local on Arch which makes it easy to wreck your installation, many projects and scripts out there only support Ubuntu and not Arch, etc.
And I say this as an Arch fan who would rather avoid Ubuntu...
You can assume whatever you want, and I'm not blaming anyone, just telling you what reasons people have for using one distro over the other. You're arguing with the wrong person for the wrong reason.
Sorry I came down to arguing like that, but I really honestly wanted to know what problems there were with the scenario you proposed. I am in devops and those are the kind of nuances I need to account for. That I why I asked for examples and felt your answer was condescending. But anyways, I can see from this thread that asking questions is somewhat frowned upon here, when the question itself is of a nature that displeases people, so I'll refrain from participating like this in the future.
Before I try to respond, you have to ask yourself: what do you imagine is the reason why Ubuntu folks have gone out of their way to patch Python for /usr/local? Surely it's not out of ignorance for virtualenv?
And I say this as an Arch fan who would rather avoid Ubuntu...