Strong sunlight, UV rays, or heat or a combination of all these can cause textiles to degrade. The degradation is dependant on these sources and also type of fibre content within the textile. Drawer upholstery that contains polypropylene yarns can harden / crack as described.
It's a bit like window nettings going yellow after some time, it's normal for some textiles to degrade in strong light / heat.
It is also fair to say that type of finishing treatment within the textile, or amount of treatment can also adversely affect this sort of damage.