Maybe a dumb question but why?
Im a firm believer that data collected that doesnt have a clear action associated with it is meaningless - and i couldnt think of an action i would take if my traffic goes up or down on my personal blog - but tbh i mainly blog for myself not really to build an audience, so our objectives might differ
There are some actions you can take. For example, when my traffic plummeted, I saw through my logs that search engines were trying to access my search page with questionable queries. That's when I realized I became a spam vector. I gave a better rundown through the link I shared.
Same reason why people have personal projects and share them on GitHub, it's fun to see people using / starring / interacting with your project / blog.
It is kind of fun even if it serves no purpose. Like those end of year recaps by various services, "oh shit I played that much Hades?"