That the risk of capture is the greatest deterrent to crime, to start? That the culprits being chased are often highly violent criminals who they don't want disappearing into the social noise? In an urban environment the number of branching permutations is enormous, so they can't simply radio ahead at the outset, and "chasing" is often simply keeping an eye on the target while supporting units move in.

There are several comments throughout this story about how police in [various enlightened areas] no longer do chases. It usually isn't so straightforward, otherwise the world's bank robbers and kidnappers will be on their way over, idling car at the standby.

What most police forces throughout the world have stopped doing is chases for trivial things (where the single most serious crime committed is not stopping for police), which has historically led to everyday people panicking when the police turn on the lights after they roll through a stop sign, etc. Police also try to resort to helicopters sooner, and abandon the chase if it's 2pm in a school zone, etc. However the nature of law enforcement means that chases still happen for serious incidents, and they happen around the world, some questionable accuracy claims in comments notwithstanding.

This is a terrible tragedy and it's unfortunate that this armchair speculation has taken the lead so quickly.