Not for this particular source. But it's visual clutter. To me it seems a bit like you're asking me to prove the colour of the car is blue, when I can see it's blue.

It's a large part of the reason why recent UIs have dropped all their border, shadows, etc. To minimise cognitive load / distractions. Proper use of white-space achieves the same effect, but with less "stuff" for the eyes to focus on or get distracted by.