If you actually think about it, it’s absolutely makes sense. The Autobahn has additional stopping lanes for broken down cars and several meters of grass to each side, which means you can safely drive hundreds of kilometers an hour while still being able to see obstructions early enough to brake in time.

Slower motorways have smaller setbacks, but still enough to keep their speeds.

City streets where you can’t see people entering the road in time to brake usually have relatively low speed limits to reduce the braking distance as well as the damage caused by a collision.

But if the visibility or braking distance are affected due to weather or broken streetlamps, it’s up to you to slow down accordingly. But even for situations like that traffic planners usually add additional signs, it’s common to see roads with signs that say

/❄️\
(60)

to warn people to drive slower when the road is freezing or signs that say

/🦌\
(50)

to warn of crossing animals and set a lower speed limit.

The same obviously applies when it’s not crossing deer but crossing pedestrians.