You're wildly underestimating how difficult it is to roll out such a change in a backwards-compatible way. It's not like Github did this today after neglecting

You're wildly underestimating how difficult it is to roll out such a change in a backwards-compatible way. It's not like Github did this today after neglecting the feature request for years; they've been on public record at least many months ago saying that they were working on it. Even if only 1% of users were unable to access a site after the switch to HTTPS, the amount of calls to Github support would be massive.