When people keep having "issues" with hotels, the cynicism flag comes up. Perhaps the same is true of corporate management. If they think someone is consistently over-petty or even trying it on, progressively reducing the amount of compensation offered may be seen as a way to discourage the complainant from complaining in future.
I suspect that most of those posting on this board do not generally have a dozen or so issues with a hotel, let alone several hotels. We travel too much and realise that a lot of stuff is just normal. I'd love to have compensation for the appalling design of some hotel bathrooms (Holiday Inn Express, are you listening?), but in the real world that just ain't going to happen.