Its FUN! ... and often develops into a rewarding lifelong hobby

Its Sociable ... music groups and societies are a great way to meet people, often resulting in lifelong friendships and  even marriage!

It develops discipline and the creative processes ... for both young and old it enhances academic learning and improves the cognitive processes.

From Surrey Arts website:

Will learning an instrument help my child's education?

Yes, very much so. There is an increasing body of evidence to suggest that children learning an instrument do better at school. Learning an instrument allows pupils to express themselves and grow in self-confidence whilst developing other skills such as hand and eye co-ordination, spatial and social skills, and self-reliance. They also develop better memories and are more likely to enjoy being at school.

Pupils make better progress with private lessons! ... Learning with a teacher privately guarantees individual focused attention, working with good quality tools

All ages are taught ... whether you are 7 or 70, its never too early or late to start!

Relaxed surroundings ... you learn best in a comfortable and relaxed environment

Better attendance ... instrument lessons at school are regarded as the lowest priority and can be frequently missed (teachers are often reluctant to let pupils out of class)

No missed school lessons ... private lessons are normally held after school, in the evening, or at the weekends

Better communication between music teachers and parents ... teachers can brief parents about what and how the child should be practicing each week.  Children make much better progress when helped by their parents

Usually better value than learning an instrument at school; often lower cost