Access to arts are vital to creating well-rounded people in society. You don't have to be "good at them" to benefit.
Fine motor control is essential to surgeons and it has been observed that for various reasons, dexterity amongst medical students is declining. Time spent wielding pencils and paintbrushes is good for it. Many other occupations need dexterity and multifunctional dexterity remains a human advantage over mechanisation/ robotics.
It's appreciating culture and history.
Self expression. (Particularly important as an outlet for healthy mental wellbeing)
Trying, experimenting, trying again in the face of "failure", developing and evaluating a concept; vital personal skills for buisness and creative skills for product development.
DS isn't "good" at art in the conventional, educational sense. His dyspraxia means holding pencils is painful and his poor motor co-ordination means his markings are irregular and messy. But he has his own style of drawing at home of busy line drawings of lots of little features added to bit by bit, and they have their own joy, and every minute that he voluntarily holds a pencil or pen is a good thing for him and supports his development in difficult areas for him. Cartoony style books make age-appropriate literature accessible to him rather than being overwhelmed by a wall of text squirming around the page.
I did GCSE art as I thought it would be light relief from options in MFL, additional science and a humanity. It was a healthy change of gear. I actually enjoyed the 10 hour exam, and the silent time to create my exam piece, I can't say that for any other subject! I have no great talent, but got a respectable grade through working through the processes of design development. I developed a pleasing style. In adulthood, I've had creative phases such as card and jewelery making. When I created resources for teaching, visual presentation was important for making information appealing and accessible.
Reducing education purely to its direct financial benefits is a massive folly.