Genuinely curious…is it rare because there are less kidnappers, or because parents are more vigilant and there is less opportunity for them to commit the crime?

It's rare because almost all kidnappings and other harmful things done to children are done by people who aren't strangers:

Aunts and uncles, parents, coaches, family friends, community leaders, religious leaders, day care employees, etc

They never seem to even acknowledge that, let alone care about fixing it.

This was known from the statistics even before these people insisted every school teach children about "Stranger danger" because these specific people are utterly incapable of overriding primal fear, fed by "news" they insist on watching, with factual reality.

Most probably kidnappers and pedophiles found a better way. Kidnapping small children has been institutionalized.

And before to say that I'm crazy or trolling, we need to remind that some estimates claim that until 300,000 small immigrant children could had vanished in the last decades after being taken by the USA government. Even if the real value is a tenth of that, we would be still talking about a very concerning and astonishing cipher

And we need to remind that ICE has happily employed some very seedy people lately. Journalists disclosed some workers with a criminal past that includes sexual assaults to minors and that wouldn't be allowed to work with minors in any other circumstance.

The sad truth is that lots of recent recordings prove that criminals are now allowed to shop for children in the streets and parks and take them somewhere with them, as long as this children aren't white. And some of this children are not seen again. Nobody in the government can explain were they went.