And whenever you do anything for the disadvantaged the advantaged (or the "not disadvantaged") want it, too. Makes it expensive.
There are also hucksters, with things like "phonemic awareness" and other non-scientific, uncontrolled-for drivel. But it makes a few administrators and university faculty feel good, so the bullying of teachers and spending of untold millions of dollars is worth it.
Then you have the fade-out of the effect of early intervention by the middle-school years.