Sure he enjoys playing his music for tens of thousands of people at a time, but do you know why else Paul McCartney keeps on touring? His July 31st and August 1st shows at Chicago's Wrigley Field grossed $10.9 million on sales of 84,000 tickets — the top concert gross total by a single performer at a U.S. venue this year.  Paul needs a little extra money for his up coming wedding.