There will be many negative comments here so let me add a positive: writing helps you think. More so than making ppt. My guess that it is helpful in some cases to force this level of detailed thought.
The purpose of presenting isn't for you, it's for audiences. The thought process or lack of it will happen either way, and can be accomplished either way.
Not really a counterpoint, but a “yes, and”: I’ve often made an “internal” presentation that is mostly for myself and maybe a few others, which distills the key concepts of something into a coherent narrative. While it can help others, I also have found the process of creating a presentation, outline, or summary helps me to properly organize (and sometimes change) my thoughts at least as much as it helps convey those thoughts to others.