Because CG only knows how to turn it up to 45, or down to -5. They don't want to hire someone who knows how to balance anything because that would make it less aggravating for players.
Look at LS Geo TB, it was "tuned" almost three years ago, before we had Relic 8 or 9. Even now this TB Relic 8 and 9 characters are getting ONE SHOT by the stupid OP garbage on defense, even in wave 1 that happens. It's excessive garbage, but they aren't going to change that or anything else they make too difficult.
Granted, if it's too easy for players, or if players find a way to beat JMK, they'll tweak the AI and even work overtime to get it working "correctly". "Oh no! Players are beating this event too easily, OT for the weekend is approved. Tweak or fix it ASAP!"