Ask HN: Why is the back button becoming more and more useless?

I have noticed that more than usual now If I click back button I never get the same page again. Neither the content or scroll position is preserved. This is true on reddit, youtube, facebook, linkedin, and other sites. Each time just loading icon appears and then proceeded by completely random stuff. I.e. I'm scroll on reddit, I see few interesting things, I click one, it wasn't as good as I thought but the other thing I read was looking good, I go back, it's nowhere now.