That's because it hides what's underneath. Thats not the artist way to go (well of course that depends). I know I do tend to use stuff like that too to "fill out the blanks", but if you think it needs a dash of realism, shouldn't he increase the level of detail rather than decrease it?
What I wanted to say was that just because the later is easier to achieve, it does not always bring extra value to the finished product.
Don't want to be mean or anything. Just spilling