From what I understand the increase in demand for labor was not to use the tool itself (which I believe would generally be water powered, not hand cranked) but

From what I understand the increase in demand for labor was not to use the tool itself (which I believe would generally be water powered, not hand cranked) but rather the tool induced a greater demand for raw cotton and provided expansion opportunities to industries that consumed cotton. So more people were picking cotton and working in textile factories.