Education does not increase intelligence. Intelligence is defined as "ability to learn". A person with 160 I. Q. may not try & not learn much. Education can help a person make more money than otherwise. Without an Ed. you might be an army private, but with a college degree maybe u could be an officer with more $ & more "perks".
To educate people. Do you mean why isn't everyone homeschooled? Because that would take a whole lot of work and I seriously doubt many parents would want to stay home all day and take care of kids. We have to go to school because we are stupid.