Because of how much more effective one on one tutoring is, it needs significantly less effort in total hours even maintaining a 30-to-1 ratio of students to teachers.
"It only takes about 50 contact hours to transmit basic literacy and math skills well enough that kids can be self-teachers from then on. The cry for "basic skills" practice is a smokescreen behind which schools pre-empt the time of children for twelve years and teach them the six lessons I've just taught you." [1]
Unless you have some strong evidence to argue why "sit down and lecture" is the most cost effective way to educate a population, I will retain my belief that it is a cargo cult at best.