Like doctors with specialties, professional appraisers and home inspectors can see things that their customer typically cannot. It's vital that both professionals be involved in the process.
Not every home inspector is truly qualified to perform an inspection. And it can be tough for homeowners to judge the professional qualifications and experience of a home inspector.
A home inspector is a generalist who identifies visible existing conditions. They are not acting as specialists in all of the different disciplines that go into the construction and maintenance of a home.