For one example, just off the top of my head, most any remotely technically-inclined young person in 2014 knows that you use Ctrl-Z/X/C/V/A to undo, cut, copy, paste, and select all. (Or substitute Command if you're on a Mac--same basic idea.) They've got that down cold, along with a host of other ubiquitous editing conventions--Ctrl-Left/Right to jump words, Shift-arrowkeys to highlight, Home/End to jump to the beginning/end of the screen line, etc etc etc. Basic text navigation and editing is a breeze, straight from muscle memory.

Then you try command-line Unix for the first time and nothing works anymore. You have to unlearn the habits of a lifetime before you can do something as simple as edit text. You can't even remap them effectively, because most of them do something else in vim or bash that you'd have to move elsewhere.

This is one of those problems that is just completely invisible to old Unix hands. It took me years to stop writing code in Notepad, because using vim felt like trying to drive a car with the gas and brake reversed, and someone punching me in the face every time I reach for the turn signal.

I'm not saying Unix conventions are objectively worse than Mac/Windows ones. Once you've got them trained into muscle memory, they're just as effective as anything else. But that need to retrain is a pointless roadblock in the path of every would-be hacker.