MIT has been uploading in-class lectures from certain professors for over two decades. A student can miss his 8:30 a.m. class and still get the exact same info at noon upon waking up. However, most universities don't offer this option. This old high school and university system is incredibly inefficient*. Worse, as the Dark Lord puts it:
Conventional classroom education is expensive, unhealthy, and unethical.
Of course, the purpose of the system isn't education but Leftist indoctrination. Also, as one commenter correctly states: K-12 is basically daycare for parents.
* Think about how much money universities could save by a) hiring only one superstar lecturer per course, and b) not having to pay weekly rent and utility costs for giant halls. From a purely economics point of view, online education would be a HUGE money-saver for these institutions. So, it's not about the money ...