While I'm not a manufacturing engineer or technician, I'd still like to give my 2 cents on this question because I've, at least, been around manufacturing clients and done engineering designs for them. A typical manufacturing building is filled with machines that help automate the manufacture of products or facilitate moving the product or materials around on the factory floor. A surprisingly high percentage of these machines are unique -- custom made -- just for that one application. They will have motors, solenoids, switches, sensors of every sort, valves, control panels, hoses, gauges, levers, rollers, and more. They will connect to electrical power, communications, water, compressed air, sanitary sewer, natural gas, and other utilities. They may be as simple as a toaster or as complex as a modern car with IC's, PC boards, or computers. Who will design, assemble, maintain, repair, modify, or improve these one-of-a-kind machines? The manufacturing production technician will of course!
In order to do this, the technician needs to be an electrician, a plumber, a machinist, a mechanic, and more. Knowledge and use of many different tools and test instruments is important as is a comprehensive understanding of many areas of physics. It's the crossroads of many skill sets in one person so the technician that can master so many areas of expertise are very desirable to have on staff.