How are you hearing no difference?

+1 to tomcarr.  Everyone hears differently, listens for different things or perhaps not as critically. 

Because people like to think that they are smarter than everyone else and that "they know better." They’re just trolls who have "be right."

It's also possible that their system are set up like some of the ones that I've seen posted on the B&W forum on FB where one speaker is sitting in a corner, they aren't toed in equally, there's a lot of exposed glass in the room...  If the whole system sounds like garbage anyway, then they won't hear a difference between cables or a DAC.

I really like the way my system sounds. I often wonder if it would sound like garbage to other listeners.

Like garbage probably not, like not much to keep talking about probably yes. 

I have witnessed a person with .99 cent cables with a pioneer receiver and swears he can’t hear a difference between cables. He compares $49 cartridges to more expensive 1’s and can’t hear a difference. 
Your system has to be of some decent quality before you can take advantage of better products. Your system will only sound as good as your weakest component.