These are some hilariously bad examples. Every Debian user I know adds repositories which violate the social contract, for proprietary drivers, codecs, etc. Ubuntu, while it's named after a humanitarian concept removed this for this very reason: it goes against making the best product possible. I'd argue that most people prefer an OS without said social restrictions and I think Ubuntu is evidence of it rather than evidence against it. That said, most of the restrictions in the things you've listed are technical or legal in nature and _do_ actually have to do with the resulting product rather than unrelated social disadvantages. The Debian social contract simply states "no discrimination" which is certainly in line with meritocracy in my view of it at least.
To answer why: because people want quality software and political agendas are a niche at best. There are much better places to address such things.
Well, now you know one Debian user that doesn't have repositories in his machine that violate the social contract, and while I'm not a purist, the Social Contract is actually a significant part of why I like and support Debian.
I don't agree with the notion that you can neatly separate "politics" from the rest of your life. Every action that you do which affects others is inherently political, and publicly distributing software is no different. By just following along, one is simply weakly supporting the status quo - which might be fine, but should be consciously chosen nevertheless.
Regarding whether I want worse software because of my political opinions, it's not really relevant what I want; I do consider having social goals as a valid position for an open source / free software project.
> By just following along, one is simply weakly supporting the status quo - which might be fine, but should be consciously chosen nevertheless.
I am not supporting the status quo, I am simply supporting the best possible software we can produce. And I don't believe we produce that by rewarding or punishing people based on factors they can't change. This is not a matter of "following along", this is a matter of using the best people to the best of their abilities, regardless of these factors.
To answer why: because people want quality software and political agendas are a niche at best. There are much better places to address such things.