I suspect that most leftists never took microeconomics in college. Too much math, too rigorous. Better to select an elective course which promises to excite the emotions rather one that will exercise and strengthen the pea brain.
They memorized a one line poem as their only exposure to economics. "From each according to his ability; to each, according to his need."
That's all the economics they know. Anyone who talks about numbers and math in economics just isn't willing to do his fair share.