"The police and prosecutors
do not want to ruin someone's life just for killing a cyclist, so they accept "I didn't
see" him or her as a valid defense (instead of the admission of negligence that it really
is. "

Most of us drive too. It is damned easy not to see a cyclist. Other than a persecution complex, there is no reason to conclude "just a cyclist" as some kind of motive, when the easier explanation is that mere negligence is a just a civil case and there is simply insufficient evidence to prove a crime. When every juror is going to hear the facts and think "there but for the grace of god go I", there is basically no way it can constitute gross negligence and therefore isn't a crime.

I just don't see the point of the many internet whines (and posting of newspaper articles) that a cyclist got hit and died, so there must have been a crime that isn't being punished. No. That is an unsupportable leap. You need more for it to be a crime.