This attitude confuses me. Looking back at things I wrote ten years ago makes me think "huh, I used to believe X and now I don't, why did I change my mind?" and "X used to be really important to me and now it's not, what happened?". If I'm writing something today I'll often look back at what I've said about it previously (and I like having most of what I've written as blog posts so that's easy).

Then there's the benefit to others: being able to look back at what people were thinking in the past is super useful for understanding how the world has changed, and textual comments are great for that.