I have a NW spreadsheet that I update monthly. I also track all my spending, even though I've been FIREd since 2021. I know it's not necessary from a financial standpoint. I could spend considerably more than I do now and be fine.
But it keeps me from fooling myself. If my spending goes up, I want it to be because I'm consciously choosing to spend more on things that improve my life, and not because I've slipped into bad habits.
Besides, it lets me indulge my own curiosity. I have almost ten years of spending data, and I wrote a program to analyze it. I can see, for example, how much my food spending has gone up from one year to the next, so I can measure my personal rate of inflation. There's no pressing reason I need to know this, but it's fun to be able to calculate it.