XLR have higher volts than RCA, and cables are less prone to interferences. So yes XLR is worth it.But that's exactly what most end users don't understand.
The device would be significantly more expensive due to the much lower sales figures. Which is because all costs are spread across much lower volumes.
Many costs also increase because of the lower quantity, e.g. housing, packaging, circuit boards, etc.
Even under favorable circumstances, such a device would be at least $500-1000 more expensive, which would not exactly increase sales.
Is it worth it just so that the power amplifiers are missing?
Another important point, with most AVR / AVPre the signals for the XLR outputs are only generated at the output. Is that worth the extra cost?