"Why Police force don't use those power orbs if they are the ones who need them the most?"
Because orbs are dangerous af for their users and you can't force every police officer to use one. If their world have laws similar to ours, I'm pretty sure you wouldn't be able to force anyone into bonding with orb (which is said to be dangerous on its own), because hu… err… beastman rights. Plus, you can't tell if orb will be useful in battle before bonding with it.
I haven't reached this explanation because the game was so excruciatingly dull, but, isn't it kind of the entire job of the police? To sacrifice their own safety for the sake of civilians? If yes then the government will absolutely want them to use them in order to improve their effectiveness at it, and if they don't want that — they won't be hired to begin with. And on that note
> You can't tell if the orb will be useful in battle before bonding with it
First of all, they don't necessarily have to be useful in the battle to help the police with their job, as it involves much more other things besides gunfights. But more importantly, you mean to tell me this world hasn't got a clue how its own rules work? For the entire time of its existence, no one bothered to conduct research to test those orbs and figure out how they function? I find that to be unbelievable.
Were you, like, reading? Orbs are simply not something to be relied on. Any sane person will use his powerful orb only in case of emergency and pay hefty price for it. Possibly die. Weak orbs may not even be worth using. And yes, orbs are still a subject of research. So I guess police of their world values lives of their officers more than insignificant ability boost (cuz, well, there are other tools and equipment besides orbs and boring police uses them instead of suicide tickets).
