I don't often write essays or letters, but when I do, I use
LaTeX, the typesetting system.
Why? Well, LaTeX produces beautiful quality that no other application manages. I have one template for letters and one for essays, and at some point, 12 years ago, I learned to use ~20 commands, and now I am a proficient LaTeX user.
LaTeX sounds like an impressive, complex skill that is tough to learn, but -- not if you have the right walk-through. I can teach anyone how to use LaTeX to my (low low) standard within 60 minutes at the most.
If basic LaTeX use can be taught in an hour, then nothing else should take much longer than that.
But it does. Often, writers prefer to teach rather than produce walk-throughs, with the laudable aim of empowering users with knowledge. But sometimes I don't want to learn, but just get from A to B so I can continue on my merry way. And even if I come to study, reading the walk-through first gives my learning experience a solid structure to build on.
You can judge the true quality of a tailor by what they can do for their fattest customer. Likewise, you can judge documentation by how useful it is for the thickest, laziest, busiest user.