[ZenGum]

In primary (elementary) school, maths is not just about the maths.

Mental arithmetic is usually one of the first lessons each morning.
Singing the tables gets kids into the daily routine, into the "school brain mode". Pencil-and-paper arithmetic is a warm up for whatever brain exercises will follow.

And at all levels, it has benefits beyond the immediate skill.
The ability to do symbol manipulation with numbers improves the ability to do symbol manipulation in any field, such as grammatical transformations of verbs, etc.
It's like bicep-curls for your brain. Pretty much no-one needs to do bicep curls for a living, but doing bicep curls will improve your ability to do whatever physical task it is you do need to do. Same with the seven times tables and your brain.