Maybe, but maybe I disagree with how they treat their female employees, or maybe I don't like that they financially support some political thing or whatever.
Capitalism doesn't work without real competition. I shouldn't be obliged to do business with this one particular company if I want to develop Free Software. My point isn't that GitHub is evil; it's that each person should be free to decide that individually.
Correct, capitalism isn't inherently evil, competitions is healthy. That's why we have github, bitbucket, sourceforge,gitlab,gitea,phabricator, and probably few more projects like this. however imagine if we had thousands and the open source community was give or take evenly distributed between them. that would simply be nightmare. discoverability will be pretty low, contributions will be even lower and the community wouldn't be thriving as it is now. path of least resistance and all that..
First you spoke of 50, then 500 (web sites), now thousands (yet you only managed to name 6).. this is starting to resemble reductio ad absurdum.
You haven't really made a convincing argument for why we might have excessive variety, such as an unusually low barrier to entry compared with other open source tools.
Moreover, I'm pretty sure your arguments could also be used in favor of federation, rather than centralization.
Why would discoverability be low? Search engines exist.
Why would contributions be low? Presumably we'd have a common way to contribute from your own federated instance.
There are thousands of websites (maybe even more!) and it's possible to discover them and comment/upload/whatever. Would it be better if they all moved to Medium, Wordpress.com and Facebook?
Maybe, but maybe I disagree with how they treat their female employees, or maybe I don't like that they financially support some political thing or whatever.
Capitalism doesn't work without real competition. I shouldn't be obliged to do business with this one particular company if I want to develop Free Software. My point isn't that GitHub is evil; it's that each person should be free to decide that individually.