Many could not find regular employment and instead, out of necessity, became non-regular workers, taking on part-time jobs or temporary work. If these people were to become regular employees, wages, productivity, and tax revenues including social insurance contributions would rise. This is desirable not only for them individually, but also for Japan as a whole.
Of course, if we set too much store by the "high-pressure economy" argument -- which suggests that labor market conditions should be kept tight through monetary easing -monetary policy may be tightened too late despite signs of inflation, potentially leading to intolerably high inflation.