Colin Flaherty often points out that this is done mostly to make the statistics look good. By making it difficult to file a police report, many crimes don't get reported, and crime rates go down. The measure of police success is low crime rates, so, this is just a good business practice for the cops.
I've heard that you should always look primarily at homicide rates if you want to know if crime is increasing or decreasing. Since the police pretty much have to take a police report when death is involved, it's much harder to fudge the numbers.
Lovely.
The guy who wrote those tweets offered the San Francisco cops a perfect opportunity to quickly arrest a car thief, and the cops declined. Makes you wonder what other requests for help they would decline.