Amateurs do microscopy because they enjoy it, professionals to earn a living. Although this simple statement is true, it leaves a great deal unsaid. Most professionals enjoy microscopy every bit as much as amateurs, though some of the sample preparation and statistical analysis may be repetitive and tedious. Professionals are necessary because there's important work to be done by trained staff using equipment that is often expensive and difficult to use correctly. As in most walks of life, professionals can devote all their time to a specialized area so that they become highly skilled and effective in their work.
Modern society depends on microscopy in many ways.
Here are a few examples. In the pathology lab, microscopists take tissue removed during surgery and prepare it for light or electron microscopy. The tissue is studied to aid in diagnosis, the patient's treatment is often based partly on these findings, so the microscopist's role is literally one of life or death. The Police - Microscopists in the forensic science lab can often help by identifying small pieces of hair, fabric or other materials found at the scene of a serious crime. A person's guilt or innocence is often decided partly on the results of such findings.