Because social programs get their money from coercion. GitHub doesn't. (To the extent that you think you can find a private company that can and does use coercion, I object to that too.)
Even as a liberatarian, I'm happy to say some things are well worth the coercion. But it should never be forgotten, because otherwise people do start thinking it's just free money that has no other concerns whatsoever, and start spending it stupidly. We know this by simply looking around at political discourse, to the point that I almost wonder if you're dissembling when you claim that nobody thinks this way. Look harder. We should never forget that social spending is a cost/benefit question that never has zero costs.
I actually personally find it a bit bizarre that people find this an objectionable statement. Realizing that money is not free and should be spent on worthwhile things to account for the coercion should lead to better spending. Defending the proposition that we shouldn't be so concerned about the costs is a recipe for producing less efficient spending, as always happens when costs are misjudged. The fact that this sort of thing has been politicized ought to lead you to wonder who is politicizing it, and what they're hiding behind it.