I agree with you. With a little bit of driving experience, you have a natural sense for what the safe speed is on a road, and that speed is almost always the speed limit, in my experience.
On a busy road with lots of pedestrians crossing, I naturally want to go much slower than I would on the same road if there were no other pedestrians or traffic. "School zones" just codify that into law - when you expect lots of kids to be crossing a road, the speed limit of the road should be lower.
The issue, for me at least, is the ambiguity. When is the school zone in effect? This creates a cognitive load. The road was clearly meant for 45 mph travel, because that is the normal speed limit. So if I let my "autopilot" brain take over, I will probably go over the 25 mph school zone limit.
It's a special case. So when I see a school zone, I unconditionally set the cruise control to be the school zone speed limit. This frees my brain from any congitive load about whether school is in session. It also guarantees that I am not influenced by the guy tailgating me.
The ability to set the speed of your car exactly, without monitoring, is really useful.
