There was a time when almost no high-end audio equipment had balanced inputs. Today, the opposite is true.
The same cannot be said about pro audio equipment, where balanced ins and outs have been the standard for as long as I can remember. The reason pros adopted balanced is easy. Noise reduction. I don't imagine the same can be said for high-end audio, so, why the switch?
I wish I had a ready answer. PS Audio started adding balanced inputs on our power amplifiers in the early 1990s because a few customers with balanced preamps demanded it. Once added to our power amps we felt obligated to add them to our preamps as well—if for no other reason than to answer the inevitable question of why one and not the other. This same logic cascaded to the sources and soon everything was both balanced and single ended.
Though we manufactured balanced input/output equipment I didn't use balanced until much later. My collection of hand picked expensive interconnects were all single ended and I was hard pressed to invest again.
Now the tables are turned. I have only a smattering of token single ended cables and everything in the system is balanced.
They just sound better.
Sometimes we fall into or out of balance merely by circumstance.
In this case, my system's the better for it.