gistfile1.txt

There are some historical reasons we cannot adopt semver. One of them is,
ironically, related to compatibility. Ruby, inside its source tree and as a
community, has had a history of making an assumption that each of the three
numbers MAJOR, MINOR and TEENY should consist of a single digit, and so many
libraries, applications and build tools rely on it. Due to this, we cannot
waste digits for MAJOR and MINOR by incrementing them so frequently, or we will
be running out of digits really soon.