Because bonuses come from developing ways to save or earn the company more money and no longer from keeping guests satisfied. Being able to shave 10% from your departments wages? You get a bonus and corner parking spot. Being able to "add capacity" to the FP+ system at no cost? You get a window cubicle and another bonus. The same thing happened with the refillable mugs. MOST people don't scheme the system, and the overall issues/losses are probably negligible in the scheme of things and can be written off as a rounding error. See how many people here didn't even know you could game the FP+ system in this manner, and if people fanatic enough about WDW to post on a forum don't know it, do you really think Joe Tourist from Podunk Whereversville knew it? But being able to show a net reduction in abuse reflects positively on someones bottom line, so some beancounter is trying to find things like this to fix.
It's the same mentality that is working so well (sarcasm is dripping from my screen as I type this) for many of the legacy airlines in the US, more seats filled and more fares = more bonus for CEO, keeping customers happy doesn't equate at all (Hi United!!!).
You have heard of my father