Because what used to be a generic indicator of distracted early childhoods (whether by nutrition, environment, weird parenting) got a new name.

And it is no coincidence or surprise that brain stimulants like amphetamines dominated the first wave of treatment. People 'perform' better on amphetamines, always have. They work so long as you concentrate on the short term and ignore long term issues like increasing tolerance, increasing demand and ultimately schizophrenia from chronic deep sleep deprivation.