Attics are actually a point of debate in the home inspection industry. The standards of practice issued by, CREAI and InterNACHI all state the inspector does not actually have to enter the attic. There are some home inspector who actually do not enter and inspect the attic.
At Regal Home Inspections, I feel it is essential to enter the attic, unless there are signs of an unsafe space such as the attic space is too small to crawl around, or the temperature in the attic space is excessively hot.