I suspect science has had more to do with the reduction than superstitions like jinxes.

Some people play lip service to superstitions like this as a form of fun or a way to communicate feelings on a topic, and not necessarily because they believe the superstitions.

For example, if I followed up a statement with "knock on wood" it wouldn't be because I believe it helps, or expect anyone to actually take that physical act (I probably won't unless to emphasize my feeling more), it's to convey I hope something succeeds or does not fail in a way that provides a lot of context in a small amount of words.

I pray to god people let go of their superstitions.

:-) Delicious irony

Jinxing means you hat people might consider the problem solved and pay less attention to it.