At some point the signal must become single-ended otherwise interference cannot be canceled. This is better done sooner rather than later in the signal chain. The purpose of a balanced stage within a circuit is canceling out nonlinearities arising in the circuit itself, and/or to double the signal level while canceling out some noise. This is purely a means, not an end. We use a balanced arrangement in specific areas within a circuit where it makes a meaningful difference. Doing this to an entire piece of equipment for the sake of using the catch phrase "fully balanced" may achieve nothing but a significant increase in cost, or worse if the two halves of the circuit aren't matched well.