It's not cost efficient compared to whey protein.
4.5oz Nutritional yeast from Bragg gets you 50g (25 servings of 2g) of protein in the entire container for $7.29. That's about 15 cents per gram of protein.
ON Gold Standard Whey gets you 1776g (74 servings of 24g) for $55.04. Thats about 3 cents per gram of protein.
An entire $7 container of nutritional yeast is also only 50g total which is actually less than an entire days worth of protein for an adult male.
It just doesn't scale.