Besides the points raised by other two commenters, the difference is also that capital gains (i.e. income from liquidating capital) is often taxed at different

Besides the points raised by other two commenters, the difference is also that capital gains (i.e. income from liquidating capital) is often taxed at different (lower) rates than job income. I think that't patently absurd, but I guess our world works according to the "might is right" principle.