The main one is to set reader expectations that any errors are entirely my own, and that I spent time reviewing the details of the work. The disclosure seemed to me a concise way to do that -- my intention was not any form of anti-AI virtue signaling.
The other reason is that I may use AI for some of my future work, and as a reader, I would prefer a disclosure about that. So I figured if I'm going to disclose using it, I might as well disclose not using it.
I linked to other thoughts on AI just in case others are interested in what I have to say. I don't stand to gain anything from what I write, and I don't even have analytics to tell me more people are viewing it.
All in all, I was just trying to be transparent, and share my work.