One can get early Alpha and Beta versions of Minecraft through the official launcher too. I think this is a nice benefit - you buy the game once and have perpetual access to the latest version, but also all the old versions which are worth playing for various reasons e.g. Beta 1.7.3 is very popular because it's one of the last versions before the terrain and cave generation was significantly changed.
Also Modded Minecraft is extremely popular, and the mods necessarily aren't version agnostic, so you need to be able to run a specific Minecraft version to play the pack of mods you're currently enjoying.
Right now I am playing Enigmatica 2: Expert, which is a mod pack for Minecraft 1.12
Today I need to teleport to my spaceship which is in orbit around a distant planet and then fly it back to our solar system and visit Mars, as I have neglected to obtain materials from Mars which I need to build this end game item I'm working on.
It's still recognisably Minecraft even though I'm working with a 9x9 crafting grid. It has internal consistency, dragons hoard rare metals, Plutonium is a rare metal, therefore make sure to bring hazmat handling equipment if you're about to plunder a dragon's hoard.
