Here are two examples of cracking due to skipping the coating step 

Some of our new customers have asked why the gallery wrap canvas prints from their previous printing company had cracks in the folds. Some even complained that the surface was flaking off in areas. This is most commonly the result when the most critical step in the finishing process is applied improperly, or not at all. The coating is the final step that increases the longevity of the image. It seals the surface and filters out harmful UV rays. The surface of ink jet media including canvas is somewhat brittle and will separate when folded if left untreated after printing. There are a myriad of products available out there that work well. The best and most commonly used are the newer Eco friendly "Aqueous" or, water based products. it can be applied with a spray gun,brush or roller. When applied, it binds with the molecules of the surface coating sealing it and giving it more elasticity. The result is a more pliable, bendable surface that is scratch resistant and nearly waterproof. Beware of printers that offer cut rate deals too good to be true and quick turnarounds of less than 48 hours. They probably left out part of the process. You can learn more about print permanence ratings at Wilhelm Imaging Research

Below is an example of canvas treated with a final coating

Canvas Depot treats every canvas print with a UV over laminate