When there is no hidden test case, if I missed some conrner case handling, I can see it and get 5 min penalty, then change the code to get AC, which is fair - I know the solution, but I missed the corner case, so I get lower rank by 5 min penalty.
But after hidden test case, sometime it's very hard for people to figure out the small mistake they made, and finally couldn't get AC, the rank will be much more lower.

I know that hidden test case is designed for preventing cheating like "if(xx) return yy", but is it the only reason? if so, the side effect will cause more people failed, less people get penalty, which should be worse on the score distribution.

Can anyone point out any other reason of hidden test case? otherwise I think there's multiple better way to detect cheating of "if(xx) return yy" rather than "hidden test case". For example, searching hard-coded test case in submitted code.