Because the dataset is incomplete if even a single city doesn't opt into sharing data, or only provides a portion of the real data.
From the FBI itself:
> Pitfalls of Ranking
> UCR data are sometimes used to compile rankings of individual jurisdictions and institutions of
higher learning. These incomplete analyses have often created misleading perceptions which
adversely affect geographic entities and their residents. For this reason, the FBI has a long-‐
standing policy against ranking participating law enforcement agencies on the basis of crime
data alone. Despite repeated warnings against these practices, some data users continue to
challenge and misunderstand this position.
That's the point: there is no dataset that will allow you to reliably rank every "major city" by crime stats because every city reports crime differently and no crime dataset also accounts for factors which may affect those statistics (eg law enforcement misreporting crimes for political reasons).
How do you even define a city in this case? You say those are normalized crime stats per 1k residents - how big are the metro areas? Are there any cities that also count a portion of their suburbs as part of the city? Does doing so reduce per-capita crime stats? etc...
My suggestion would be to thoroughly vet your sources before posting their conclusions as fact.
No I didn't. I've been working with UCR data for 10+ years and I recognize it in the wild. Furthermore, my points still stands regardless of the source: "there is no dataset that will allow you to reliably rank every 'major city' by crime stats because every city reports crime differently and no crime dataset also accounts for factors which may affect those statistics."
If you know where their source data comes from and why its so accurate, feel free to educate me. Their own site says this:
> Q. Why rank cities on safety even though the FBI cautions against it?
> A. This report and/or our data cannot and should not be used as a measure of the effectiveness of law enforcement due to the myriad factors that can contribute to crime in a community.
EDIT:
There is no mention of UCR as data source, where did you get it from?
https://www.neighborhoodscout.com/about-the-data/crime-rates