It's unfair to those speaking a different language. There's also the extinction of other languages (and all the work that went into them, and all the works that used them, literature and associated culture). It's like the extinction of species in the rainforest, except for memes (in the original Dawkin sense).
The reason is the network effect, in that the more people who use a communications system, the more valuable it is (given that communication is valuable). Language is a communications system.
This forms a natural monopoly: because of the value of larger networks, it is inevitable that one language will dominate - unless there are other barriers partitioning the network, akin to the lack of a telecommunications physical layer in centuries past.
People in the world speak several different languages. When they want to talk in a way that will be understood in many nations, they utilize a language widely known, at least to the portion of the society that is more literate. At a time it was Greek; later it was Latin, then French. Currently it is English.
I completely disagree, Github.com should NOT be localized.
I agree that making sure your language doesn't disappear is important, but it has nothing to do with Github. It is your job on a day to day basis.
Having localized versions might lead to messy projects having multiple languages in issues and everywhere. It will not help the open source community as a whole but dilute it. It may be sad, but English is the language of IT and I think it will just lead to a wider and better community to all talk a single language, whatever it is.
Plus, managing multiple locales in an app just sucks, it will lead to problems, they would have less time to work on feature which is the point.
Maybe a localized version of Github Enterprise would make sense, but certainly not Github.com.
As a bad analogy - It's like asking everyone to ignore other programming languages because C++ is popularly used and the others are not (even if they are more elegant and better structured)
It makes far more sense for 7300 cultures to learn one additional language than for 7301 cultures to learn 7300 languages. The former being difficult, and the latter being impossible.
The reason is the network effect, in that the more people who use a communications system, the more valuable it is (given that communication is valuable). Language is a communications system.
This forms a natural monopoly: because of the value of larger networks, it is inevitable that one language will dominate - unless there are other barriers partitioning the network, akin to the lack of a telecommunications physical layer in centuries past.