Why was Paul's parents so eager for Paul to learn music?

Paul's musical education is very important to his parents because they both play the piano.

Paul's mother tells him how important it is to his father that he study piano, as his father regrets that the War prevented him from becoming a better pianist.

http://www.gradesaver.com/maestro/study-guide/short-summary/

http://www.gradesaver.com/maestro/study-guide/section1/