outdoor cats kill little animals like birds and rodents. Escaped powerful dogs kills cats, small dogs, little kids and the elderly. I've read too many horror stories about pitbulls and other dangerous powerful dogs.
They can do pretty decent damage to healthy adults too. I got attacked by a couple of larger dogs a few years ago (technically not pitbulls, but a related breed I'm not sure), had to get surgery and couldn't do my bullshit deskjob for like a month. Any physically intensive job and I would've needed 6 months off work. Considering what dicks employers are I wouldn't be surprised if there are people who end up homeless because someone forgot to close their backyard gate one day.
I just really don't want my kids around any dogs, which is why I disagree with just letting any of them roam. A dog snapped at my kid's face and now we're both afraid. Dogs just aren't people. They get upset and bite. I don't mind people having them, but yeah.