Being able to do basic math in your head is valuable just in terms of basic practicality (quickly calculating a tip or splitting a bill, doubling a recipe, reasoning about a budget...), but this is a poor analogy anyway because 3x2 is still 3x2 regardless of how you get there whereas creative work produced by software is worthless.

I encourage you to reconsider.

Mental math is essential for having strong numerical fluency, for estimation, and for reasoning about many systems. Those skills are incredibly useful for thinking critically about the world.

To a certain point. Basic arithmetic is important but the ability to calculate large square roots or multiply multi-digit numbers is not very relevant when you can trivially calculate them on your phone in seconds.

That's simply not true. I use mental arithmetic skill every day. It's irritating or funny when you come across someone who struggles with it, depending on the situation.

Obviously basic levels are needed but the ability to say multiply 4 digit numbers in your head is totally superfluous. Theres a parallel to software engineering there.