As for why wages aren't growing, there's many reasons. For one, automation and increases in efficiency undercut wages. In economic terms, income from capital is increasing faster than income from wages.
Second, immigration. For example, in Canada, if you can't fill a job at a certain wage, you can bring in temporary foreign workers or sponsor an immigrant. This means the wage of that job will never go up because if the labour market is tight, you can simply draw from another labour pool. The US and most western countries have been affected by this.
So on one end you have less need for labour and on the other, a limitless labour pool. Low 'unemployment' stats don't necessarily tell the whole picture since low wages drive up employment, but because the demand for that labour is only at that wage, it doesn't put upward pressure on wages.