Why is it some home inspectors don't go on the roof? The main reason is there are no requirements in the standards of practice of the national associations for a home inspector to go up on the roof in order to inspect it. Those inspectors who do walk the roof want to be competitive and get a closer view of any issues. Getting onto the roof is a personal decision made by each individual home inspector. Other factors play into a home inspectors ability to get on a roof. For example, the roof may be too steep, made of fragile materials that would be damaged if walked on, or slippery from ice, water, or snow.
Inspection from the ground using binoculars is very effective. The type and condition of the roof surface can be seen from the ground. A good pair of binoculars will help in getting a closer look at details such as the flashing around chimneys and any other roof penetrations. Inspecting the roof from a ladder will also help. Some inspectors even use flying drones with a camera attached to inspect the roof.
Personally I get on any roof possible to get a closer view but don't judge those who do not.