Computers and other technological advances have been responsible for the increased productivity, not the workers.
I'm afraid you're somewhat mistaken. Workers have been responsible for the increased productivity, just a different type of worker. It takes workers to design a computer, build it, write the programming, operate it, maintain it, etc.
And the work they do - or have already done - displaces (or displaced) many more skilled, often educated workers with far fewer skilled and semi-skilled ones. Consider a function as manpower consuming as payroll processing once was and how many skilled workers have been replaced by their computer. Consider how many workers have been replaced by automation. How many tax returns are done on-line instead of in-line at Taxes-R-Us? Most didn't find work designing, building or maintaining the tools which displaced them. The work they once did is still being done but not by workers and at a far more productive rate.