This reminds me of when Slack shutdown its IRC bridge [0], and in a pretty negative way. I get that usage is down, but that tends to happen. Supporting niche users is how you win customer goodwill. The active users of SVN on GitHub clearly aren't going to switch to git, and I can respect the maintenance costs, but they're probably just going to switch to a different provider. For them, their workflow is now in-danger and they have to solve that problem in-addition to whatever they're working on. I always thought it was a lovely little feature GitHub supported, and I'm sad to see it go for this reason.
[0]: https://it.slashdot.org/story/18/03/08/2049255/slack-is-shut...