Making art isn't always the cakewalk some-to-many nonartists think it is.
When an artist dude (say, for example, me) is a representational painter, one might think all we should have to do is paint what's there. Some realist painters do that -- every leaf, every blade of grass, every feather, every hair...whatever.
Problem is -- that slows down the process a lot, which means the painting takes longer to do, and a higher price tag has to hang from the finished piece.
Perhaps more importantly, a painting where every square inch/square centimeter is sharp and detailed can be hard to look at. If you look at the Old Masters, you may notice most of the edges are softened and blended EXCEPT for a spot the artist considered most important--that spot will be sharp and often contains the area of highest contrast -- the darkest dark and the lightest light -- within the work. The sharpness and contrast tends to draw (no pun intended!) attention to itself. In essense, the artist makes you want to look at the important feature in the work.
The attached image is "The Adoration of the Shepherds" by Guido Reni from the National Gallery, London. The painting is detailed throughout but also features softened lines and relatively dark colors throughout -- except for the infant Jesus. He is the lightest, brightest area in the piece, and I suspect (not having seen the original) probably has the sharpest detailing of the entire painting. How can you NOT look at the cute little guy?
There you have it -- your art lesson for today. A good painting is more planned than you may have thought. And doesn't it just make you feel all warm and fuzzy to know that you've been manipulated by the artist to look at what s/he wanted you to look at?