Not everyone is a certified genius like Grigori Perelman who can do great research while living in a vacuum. You need great advisors who will guide you, and fellow grad students who you can ask for help and bounce ideas off. The academic enviroment is invaluable for someone doing their PhD, and it's pretty much impossible for someone with somewhat above average intelligence (and let's face it, most PhD's are not geniuses) to do good research with just a computer.
The "all information is free and you can study anything using just a computer" is a stupid meme that doesn't work for the vast majority of people.