There is a lot I could talk about it. But first of all, not all regions in Brazil don't use "tu". Some do.
In some regions (not many) they use "tu" with the correct verbal form. In many other regions "tu" is used but they put the verb in 3rd person (which is wrong, like in "tu vai"), sadly this is what you find in most places.
Most Brazilian just don't understand what is the purpose of the 2rd person in singular (tu). Some think it is an erudite form of treatment, some think it is old Portuguese, some even think it is a formal treatment pronoun, It all is very sad...