A reference for me. And hopefully for you.
I forget how to do things extremely fast. I end up having to reference my notebooks often, or visit the same tutorials for the same snippets of information. Even then, I end up making the same mistakes, and getting stuck at the same spots very frequently. Thus, I decided to write down (in no particular order) tutorials on doing the things I do (with no particular subject matter).
It also helps that stuff looks good when typed up.