As a tourist a few years ago I needed to provide a CPF to buy soccer tickets online in Sao Paulo. Intercity busses also required one to book online. Neither accepted anything else like a passport. It was... inconvenient and not optional for those things!

they relax this during the f1 weekend. it's kinda of a joke.

already considered a paypal-like service just for foreigners, but then figured criminals would use it instead to evade tax/etc.