If you're at the level where you can write a decent book on programming or something... that means guaranteed job offers for the rest of your career.

Like, I haven't seen Raymond Chen's resume, but if he calls me up tomorrow looking for a job, I'll find something for him, even if we're not hiring.

Ditto for Steve Klabnik, Carol Nichols, and some other people in the Rust community.

Engineering and writing/communication/organization is basically the definition of a tech lead. If you find me a good engineer with good communications skills, I'll get you a mid-6-figure salary no question.

I'm pretty sure it does, but I'm also pretty sure it's okay if it doesn't.

You don't need to get paid directly for those skills to be valuable.

I started brushing up on my writing skills since at the higher levels of engineering (and prob all other fields) communicating your ideas more effectively will open up way more opportunities down the line.

Some of those may have monetary rewards. But the reward can be something else as well

According to legend, a new student of Euclid’s once asked him, “What shall I get by learning these things?” In reply, Euclid beckoned his slave and told him, “Give him a coin, since he must make gain out of what he learns.”

Depends what those two or more skills are.

You might be a top flight musical basket weaver but that won't pay too well.