There were plenty of cases where in app notifications lead to people getting tested and in touch with their local tracing efforts. You don't need privacy invading levels of analytics to measure that. With the low numbers we had over the past months exactly what else do you expect?

I had several notifications of low risk exposures, so the app is fed with some data. This doesn't happen in the Italian version of the app if you are living in some regions, for example.

If the app is useful, this is another topic, but it was not the point of this thread.