Earlier quoted context omitted.
Because it's appropriate and descriptive?
We're actually dumber than the frogs. The original 19th century experiment involving frogs that didn't jump out of heated water was using frogs who had had their brains destroyed. The question being asked was whether the escape reaction to hot water was caused by the brain or by something further down in the nervous system. With an intact brain, the frogs would jump out. Without one, they wouldn't. Question answered.
The frogs have it easy. All they have to do is jump out. One individual action and they're safe. (Until the scientist catches them and uses them in more experiments, anyway.)
The situation for people living under governments becoming gradually more oppressive is much more complicated. You don't know for sure that the water will keep heating up. Escape is extremely difficult and costly. Turning off the heat takes massive collective action. A third of the frogs actively want the water to boil, and another third don't really care.