What's wrong with most police not having lethal weapons? If police are in danger, they can request SWAT backup, specialized firearm users who won't shoot in unw

What's wrong with most police not having lethal weapons? If police are in danger, they can request SWAT backup, specialized firearm users who won't shoot in unwarranted situations. Regular cops could even have tasers or rubber bullets to deal with threats in a less destructive manner. Why do they need lethal force for helping their own citizenry?