I think that it’s because the scalp itself gets dried out from too much washing, so the glands respond to that.

When the scalp skin “normalizes” the hair slowly normalizes as well, since the oil travels down the strands.

That’s my guess. I went from shampooing daily to every other day and at first I would get an itchy, gummy scalp. But eventually that gummyness worked it’s way out. Every time I shampooed I would get that dry, gummy scalp the next day.

So eventually I shampooed less and less. Now I don’t shampoo at all. I just rinse daily with water and massage my scalp.