That's probably because of Brazil's strong history in F1 - Fittipaldi, Piquet, Senna, Barrichello, Massa etc. Australia and the USA for example have far less history in F1, where it's seen as "boring Euro w@nker racing".]
That's astonishing. I'm from Brazil and here autoracing is the elite pastime par excellence. Most of those famous drivers are rotten rich...
Here in Australia motor racing is also generally seen as a working and middle class sport, with the V8 supercar sedans being the favourite of the working class masses. Ironically almost all of the drivers use the bike as their main form of fitness, to the ignorance of the fans.