Being healthy lets you live longer. That’s a good thing; live is generally a pleasant thing, and much better than the alternative.
Being healthy is also cheaper. Having medical issues may turn out to be very expensive – especially as one gets older and puts a lot of mileage on the body.
Physical training helps compete in cognitive tasks. Being physically agile makes you mentally agile. Increased metabolism improves blood circulation to the brain, enabling better work.
Overall, it’s a time saving, rather than time cost, to work out or participate in sports. My favourite one is jiu jitsu – it’s very intellectually stimulating, and it doubles as a self-defense mechanism. But you can do anything else, from soccer to basketball to running.