A lot of these changes are very small, but they are meant to work on a subconscious level. A good example for me is fixed width font. When programming, I find some fonts to be pleasant to work with, and other unpleasant. It's not a extreme reaction, just some font's "feel" better.
It's a very subconscious thing, how we appreciate two similar things with slight changes, and often we would struggle to explain why we feel that way. It just 'feels' better.
