This prevents fat-finger mistakes. You could go further and try to prevent cat-on-the-keyboard mistakes, which is maybe what you're describing (solve this math

This prevents fat-finger mistakes. You could go further and try to prevent cat-on-the-keyboard mistakes, which is maybe what you're describing (solve this math equation to prove you are a human who is sufficiently not inebriated). Or even further and prevent malicious, trench-coat wearing, pointy-nosed trouble-makers. The point is, yes, it is possible. That's what good design does.