There's a longstanding bias against tone controls in high end components. Partly this is due to the fact that they're often poorly engineered, and a poorly designed tone control probably will due more harm than good. Any component that operates in the digital domain should be able to perform basic DSP, like tone control, very transparently.
I will say that I've really no use for tone controls, but there's no reason they can't be added to a fine preamp or int amp. Especially if a bypass is also included.