Speaker manufacturers ? To my simplistic way of thinking, there shouldnt be a huge chasm between the ability to build a good preamplifier and the ability to build a dedicated headphone amp - always happy to hear otherwise from Ray or someone who knows that of which they speak.
Speaker gear manufacturers.
But for the longest time, they have ignored our segment of audio...and no there isn't a huge chasm, but for some reason they preferred to not even try. Don't get me wrong, I am very happy with "our" gear manufacturers like Ray Samuels, or Woo Audio, just nice to have others offer more selection.