Taser != Magic Bullet
The problem here is the police think, like all uninformed/stupid (classify 'em how you like) people, that new technology are magic bullets and foolproof. When electronic keys for cars came out (most of them are rfid, I think, but I'm not sure), insurance companies thought that now cars couldn't be stolen since they needed the original key. Some people, however, were able to obtain master keys and copiers, and stole expensive cars. When the owner tried to get their money, the insurance companies refused because they saw the keys as unstoppable.
The cops believe the crap the taser companies are feeding them, and think that they are not lethal, and should be used at every opportunity when facing a violent individual, as opposed to guns and batons. Little do they realize the implications and effects such a weapon has (I'm sure there are training programs, but when have training budgets ever been good?) and so they use them, believing that they are doing the right thing.
High voltage electricity does not exist naturally in humans. I'm assuming it's not a good thing for us; please stop believing in your magic bullet.