[khedoros1]

Google has the reputation for trying to hire well above average developers. If some fraction of professional software developers/engineers don't have the aptitude to get through the interview, regardless of preparation, then it should be fair to assume that the other candidates with the aptitude to be hired might need various levels of preparation, depending on past experience and their own level of ability. Those who are already prepared by aptitude, education, and experience, won't need to study. Everyone else will fall a little short, and have to put forth some remedial effort.