The state of São Paulo has this annual report called Perfil do Roubo that shows what were the objects taken in thieves. I live in Brazil and I can affirm this report represents other Brazilian cities as well.
According to the 2021 report, 40% of the occurrences included the victim's documents. Only 10% of the occurrences exclusively targeted the victim's documents.
They're not interested in your passport. You don't need to worry about that 40%. Brazilians carry their national ID card in their wallets, and that's why the numbers for stolen documents are high.
So keep your passport somewhere safe. Not in a bag someone can take from you. I usually have one of those "hidden" money belts I keep my documents in.