From time to time we see window lettering, vehicle graphics, and business signs looking tattered and just plan worn-out past it's prime. This cracking is the result if years of element and sun exposure to the material - vinyl films.
A bit on vinyl films. There are several different manufactures of both cast and calendared pressure sensitive vinyl films, all of which bond to surfaces with a thin adhesive film right on the material. The cast films will give you much longer life than the calendared films. Don't be fooled, they look and feel identical, except in price. If you want longevity always seek out cast, or high performance films. They will crack overtime but hopefully a lot less than what you are witnessing here.