Touch-typing. It's difficult to relate to if you cant touch-type. Expert typists loathe taking their fingers off the middle row; using the arrow keys(or any other navigation keys) means taking your fingers off.
For this demographic, HJKL is just wrong.
Computer gamers are also proficient in controlling a keyboard and a mouse at the same time, so the home row argument does not apply.
j still moves you in the same direction as ctrl-j (linefeed)
h still moves you in the same direction as ctrl-h (backspace)
there's never been a good association between k or l and their ctrled equivalents; no gain or loss there
u is now up - mnemonic ftw
moving undo to ctrl-u would make redo (ctrl-r) more discoverable
Of course, already having muscle memory for hjkl from vim, robots, hack, &c, I'm not rebinding anything standard - I find it valuable to be sufficiently at home on any system I am I find myself working on.
About those keys - with the possible exception of S - all those keys are tied to significant functionality you wouldn't want to replace.
Gamers are proficient in their niche; game playing. However if the job is to hammer out 400 lines of code or a manual, I'd back an expert touch-typist proficient with Vim over a gamer every time.
It's difficult to explain; the kind of people I'm talking about are experts in not just typing; they are super-proficient in coding as well. They have the text in their head, they just want to feed it to the computer in the shortest time possible. I've sat and watched an Unix guru create a program from scratch with Vi - it's a marvel, it's quite like watching an expert race car driver, if you're into that sort of thing.