It's not something one really notices in the day by day, but if you ever go to a department store/train station/anywhere busy, and just take a moment to observe all the details, you realise just how much stuff there is overlooked. That was one of the things I first realised when i started working backgrounds, just how much extra stuff you have to add to make it look "normal"

For that picture specifically though all of what I said above, but also I was learning the perspective tool at that time and rendering metal is ANNOYING.