At this level of high(er) end audio why not offer balanced connections?

Some of the best sounding components ever made use only RCA.   The fact that a component has XLR does not mean it's "better"  .   My last preamp, Zesto Leto had a full set of both RCA and XLR inputs and outputs.   Aside from the difference in gain it was hard to tell which format was being used.   They sounded identical 

Andrew Robinson uses only RCA connections. He is not a big fan of XLR ....

I only know me truly high end manufacturer who does’t - Spectral - and they d sign their system end to end  - you need their cables! Boulder requires XLR , and Ayre includ s it, DCS, as well.

Ayre’s Charlie Hanson was a big advocate of balanced connections. Ayre’s user manuals state that balanced connections are preferred. Of course Ayre’s components are fully balanced, so a balanced connection with them makes sense.

My tube amps are from Triode Audio of Japan.  TRX-M845 mono blocks.  I asked them directly what type of cables they use when setting up systems at major audio shows.  My thought being they would use what makes their equipment sound the best.  They responded only RCA cables are ever used, as as the amps are not balanced by design.  That's good enough for me.  As for the "long run" cable scenario. my preamp is 18 feet away from my amps.  I have been told by many sources this distance is nothing for an RCA cable.  Now Hegel on the other hand, suggests the use of high quality XLR cables is the way to go.  I have tried both and must say I hear no difference in sound.  Tempest in a tea cup IMHO.