Your own source says:

“In 2012, the National Crime Survey – which supplies data to the ONS – reported that there were roughly 608,000 theft from a person incidents across England and Wales, which was a high for the decade. However, since then, theft from person cases – including those including smartphones – have fallen year on year. A key factor for this continual decline could be that smartphone security has improved to a point that it’s no longer worth stealing them; with Face ID, trackers, and fingerprint scanners, it’s now harder for criminals to wipe and fence stolen property. It’s also possible that, due to the ubiquity of smartphones, the desire to steal them has simply decreased.”