Because an advanced economy does not work as you are proposing. We have 7% unemployment rate if you put all these people at work in manufacturing we still cannot satisfy our demands.
Manufacturing jobs create about five jobs outside of manufacturing for one manufacturing job. This would certainly help with unemployment. Take Sirius radio for example...they are in trouble partly because of the car situation...Sirius radio comes with many new cars. Tech makes many of the chips used in modern cars. Parts suppliers play a role. People who have decent jobs buy things from retail and eat at restaurants...it’s all linked...making things produces wealth...consumption type economies don’t create wealth.