That is, by far, the important thing.

Most definitely.

...but then cops would have to think and defend their conclusions, which isn't likely to happen.

Right. Even my father mentioned that they default the blame to the person behind because it is that person's fault 99% of the time, and it is easier than trying to argue and find facts to prove the innocence of the 1% that aren't at fault. So, that 1% gets blamed anyway. And, of course, that 1% is a very grey area, so it seems to make sense that they would operate this way. I'm very sure those statistics are better than those of other laws.