They initially offered it in the store, and that buggy release crashed some PCs, including one of mine, on install. It then encouraged us to reinstall Windows from scratch, losing data, even though it was possible to recover back to Win 8.0 without data loss. It was a mess.
They later moved it to Windows update, where it automatically installed correctly even on PCs that were screwed up by the Windows store 8.1 release, so I think you're imagining something that's not the actual reason, and the real reason was to drive traffic to the nearly-useless Windows Store.