How can anyone fail the signal test

When I was taking the signal test (or waiting to take the test), I observed a number of individuals who failed the test.

I just couldn’t believe it!

How can somebody fail to identify signs that we see on the roads on a daily basis. Signs like no u-turn, no right turn, speed limit 80 km/h, speed breaker ahead, no parking, it doesn’t matter we follow them or not but don’t we all recognize these signs?

How stupid one has to be to fail the signal test? And that also computer based where you have to select the right answer out of three choices.

And if someone fails the signal test they certainly don’t deserve to drive a car. You must be able to understand the road signs before getting your hands on the wheel.