Balanced connection/amplification for phono?

Here's a poser I don't know the answer to: Phono cartridges are inherently electrically-balanced devices. They output an extremely low-level signal, which must then be carried on low-loss cabling (both within the tonearm, where cabling must obviously be lightly constructed, and the interconnects leading away from the 'table, where demands of optimal signal-transmission can be at odds with the use of heavy shielding) and pre-preamplified to a high gain factor, both areas susceptible to signal degradation via environmentally-borne RFI/EMI contamination. Yet despite the importance of maintaining high signal-to-noise ratios in these wires and circuits under difficult conditions, few turntables or phonostages offer fully-balanced connection and topology, and most audiophiles must connect and amplify their naturally-balanced phono cartridges in single-ended mode while employing relatively noisy, lossy RCA jacks. Why is it that phono connections and low-level preamplification aren't routinely carried out in electrically-balanced mode, so as to take full advantage of the penalty-free (aside from cost) noise-cancellation properties (regarding both signal transmission, and self-noise/distortion of the high-gain amplification) enjoyed by complementary circuits? This would seem to me to be an easy conclusion, and yet it's something fairly rare to find. Can you guys enlighten me as to why this should be the case?