Let me start by stating that touch typing is orthogonal to coding well.

The nice thing about touch type is to not think about typing. One quick glance to position your hands on the home row (there’s helper on F and J), and then whatever you want to write just flow out. While I use two thumbs to type this on mobile, I’m mostly using my peripheral vision. Typing on a real keyboard is better as I have better feedback and can use all my fingers.

It’s only one reason: No need to think about typing, it’s all muscle memory.