It was a leave of absence according to Wikipedia.
Yes that's what made him what he is today, but dropping out is not the same as never going to Uni, a big part of the college experience is getting to know yourself and it really helps people figure out what it is they want to do with their lives. For me just my first few months at Uni was a huge eye opening experience.
Also he met Paul Allen at Harvard, co founder of Microsoft.

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“Society is like a stew. If you don't stir it up every once in a while then a layer of scum floats to the top.”