I wondered that, too, in the beginning. I don’t wonder anymore, but the bigger question is what to do about it. And I do not know yet.
https://www.nationalpitbullvictimawareness.org/
If people would only look at ER stats for dogs bites and ERs. Hugely more pit bull attacks and fatal ones.
http://enhs.umn.edu/current/6120/bites/dogbiterisk.html
https://www.caninejournal.com/dog-bite-statistics/
And the ER visits by dog type I couldn’t find because I don’t have time and you should do it if you think pit bulls are benign.