True, but effective tac-coms, common sense, and locking down points of entry can deter most attempts. Often times I see 8 officers stacked in one spot not paying attention to a parachute vest falling right in front of them.
I remember having to process folks from Synergy, Bad Blood, Regiment, Dark Horse, and other tough gangs. You were lucky to get the suspects to the HQ, so you needed to have a decent battle buddy or at least a plan that you could get across to a handful of cops to help out. These days the APD would rather play like a bounty hunter than a cop.