I bet people would much prefer a brushed aluminum or SS face plates and knobs with a more attractive power button or light, especially a blue light since many of todays equipment has gone the blue route. It would be a nice tweak for great equipment. He might sell more. I talk to a lot of people on other forums and when they see I have VA equipment they complain of the 1970's generic look. A lot of people want the eye candy appeal as well as good sound. And they pay for it too!
Frank tried silver faceplates. I have an older AVA preamp with one, and I prefer it over black. However, hardly anyone bought them. Everyone wanted black. End of story.
As for fancy faceplates or switches, or silly blue lights - I don't want to pay for them. I just want durable, reliable equipment that sounds good and doesn't require that I take out a second mortgage to pay for it.
In addition, the craftsmanship of the faceplates and cases that Frank uses is excellent. Yes, the look is simple and conservative, but there's a beauty to that kind of thing too.
Finally, I don't give a good god damn about the way the things look while I'm using them. I listen to music, not gaze lovingly at the sexy curves of my amplifier that 9 out of 10 slick magazines recommend.