One of the negative changes in the lives of children during the past two or three decades has been the increasing pervasiveness of entertainment that is completely passive, or that requires a machine of some kind to interact with the child. While coloring books do not get the child out of the house and moving around, they have some very attractive benefits.
Anyone who thinks that the pre-drawn lines in a coloring book limit creativity, should observe two children colorings separately on the same picture in two identical coloring books. Not only will the two renderings be completely different, but the manner in which they have been done will offer insight into the personality of each child. One of them may stay strictly within the lines while the other may almost completely ignore them. One may use soft pastel colors gently applied, another may use bold colors applied in vigorous strokes. Some children will experiment with shading and other techniques without having it suggested to them. Occasionally an older child will even draw a simple object, free-hand, for a younger child to color in.
There can be some frustration in coloring, or any other sort of artwork, for the child who sees better quality in the work of an older child or a parent. This offers an opportunity to teach the value of continued effort. A parent or teacher can make a point of saving the child's earliest efforts for comparison at a later date. The child who is told about this plan will have an incentive to continue coloring, and will take pride in the improvement she sees when comparing the later to the earlier efforts.
Children who use coloring books are more likely to engage in additional creative efforts. It's important that youngsters think of creativity on their own part as a natural element of life, rather than expecting everything to be ready-made for them. The lines in a coloring book merely provide a jumping-off point; it is the child who makes them come alive.
When my own children and I spent rainy or wintry afternoons gathered around the table with coloring books and a pile of crayons, I avoided comparisons and competitions as to whose achievement was the "best" and I let go of any inclination to criticize or suggest improvements. The quiet and peacefulness, combined with the un-demanding nature of the activity, was therapeutic for all of us. Many years later I now see the same thing happening as my grown-up grandchildren sit and color with THEIR little ones.
This is another nice thing about coloring books: Despite occasional changes to materials and subject matter, there is a continuity from generation to generation in the basic method of coloring and the setting in which it is done. With everything else changing so fast, I believe it is valuable to retain some things essentially as they have "always" been - things that children can count on for a sense of security in an insecure world. Coloring books provide one of those dependable facts of life that will be there even when so many other things seem uncertain and unfamiliar.