Why pit bulls, other ‘dangerous dog’ breeds aren’t banned by elected leaders

The problem is you can't tell which large breed of dog is dangerous, and that is why people get attacked and killed. In general, people are not responsible for their dogs, and let them roam around the neighborhood. For a pedestrian walking in the sidewalk, they are a nuisance, and potentially dangerous. In situations where society is not up to par in responsible ownership, the city, or state should step in, and address the issue as the consequence of the deficit. I know a pit bull breed that is a nice dog, but if that dog is let loose in the streets, she will bite people. Ultimately, because of this issue, the question is, do we need big powerful animals as pets?