1. How will kids know if they will like 'coding' if they never try? School should give kids a little taste of everything so they can make an informed decision on what kind of work they want to do when they grow up.
2. They say it takes "10,000 hours to master a skill". That's easy when you start as a kid: most Disney animators spent countless hours doodling as kids, most best selling authors wrote diaries and short stories as kids. Likewise, the best computer programmers tinkered in BASIC on personal computers as kids. With that kind of background, learning art, writing, or coding in university becomes a lot easier than starting out fresh later.
3. Even if they never pursue a career in coding, coding can be fun. Many STEM camps let kids create their own fun little video games, or control their own robots in friendly contests.