This guy learned how to make a 16-bit ALU (Which in my opinion is a great amount of experience) and got a job offer from playing a game on his spare time.

Hackers that play video games want to learn and try out different things with the game, not only play it. I myself am really interested in how the game is saved (How chunks is designed, etc.) and is now currently studying linearly interpolated 3d perlin noise on my spare time because that's how Minecraft design the dynamic world.

Hackers that have decrypted or learned how the game is saved will make tools to ease work, and/or to visually view their world, or to see it from a different perspective.

Minecraft has made hackers design map-editors, cartograms and other things, including a 16-bit ALU in-game.

Making programs and learning how stuff works is a net gain for the community.

Correct, it was someone else... but people like him just want to see things like this succeed so it was net gain for everyone. And it really isn't about video games (I haven't played any game except for some Wii for the last 5 years), but just pushing the limits of what we can do and learn. I see Minecraft not as a game, but as what a single person did through great imagination and effort.

encouraging more people to play video games is hardly an especially worthy goal

Neither is Facebook, Twitter, most of the development we talk about here, or basically a million other things, but doing things to push the boundaries of what we know are.