The reason we become experts as something (interacting with a computer here) is that we spend time thinking about it. By making user interactions harder, we're actually training people to think in a way that will allow them to extrapolate simple solutions to larger problems in the future.
Knights-in-training learned with heavier swords than they'd use in battle, so that when battle came they'd be able to wield their swords effortlessly.
most people don't want to be knights, they want to be the people who are ordering the knights into battle. (most computer users don't want to become experts at interacting with a computer, they want to be adept at using the computer to do taxes, interact with colleagues, search for information, etc.)
Most knights-in-training also had other ambitions. But they wanted to live through the battles.
How many people have had their week ruined by a lack of version control? Not geeks, but real people who didn't even know what that was until Dropbox arrived.
And version control is old hat. What other computer tricks are there? Backup? Deployment? Putting services in the cloud? Building services? This isn't stuff that requires a PhD in algorithms and distributed systems, just stuff that requires basic competence.
Exactly, that's why UNIX is for knights! Those who use it (at least, via the terminal) eventually become knights, and it's through that process that the curve shown in the article develops.
Knights-in-training learned with heavier swords than they'd use in battle, so that when battle came they'd be able to wield their swords effortlessly.