I know you're not guaranteed to be a football player from playing footie at school but it gives you fitness, team skills etc
Let's look at this rationally. It takes around 10,000 repetitions to get something into your muscle memory. It's easier when you're young. For athletic arts yes both athletic and arts such as classical ballet, other forms of dance, and playing an instrument, the advantage of starting to learn young -- at about 8 or 9 is incalculable. It's because these require very fine, minute motor skills, using very tiny & precise muscular controls and a deep connection between muscles and brain.
Just ask anyone who's tried to learn an instrument or learn to dance as an adult.
Whereas "team sports"? Unless you've got a child showing the potential as an Olympic athlete, a lot of sports skills involve only the gross motor skills, and don't require the precision & delicacy of music or dance training. They can be learnt much more easily in later life. It's pretty easy to "learn" to jog and run a marathon at a much later age.
Ah well, if you're determined to be completely unreasonable and ignorant to boot, I suppose that's your loss. But the real sadness is, it's your DS's loss most of all.