I'm no cop, but, I'm pretty sure they have rules of engagement regarding what they can use depending on each situation - or at least I do know 100% that is how it works in the SAPD here. It's like a tier system of what force they can use, officers here carry pepper spray, tasers, some have nightsticks and then, of course, handguns.
Now keep in mind I'm not saying they use any of it properly