As you probably already know, it's about a lack of colorations. All external cables that you plug in to or between system components have the potential to do one or the other. However, i do not believe the superfluous claims made my cable manufacturers regarding specific tonal changes or "improvements" because they have never heard your system. What works in one system may not work in another... synergy is important.
Cables can also tame the sound of sharp snares or otherwise unpleasant passages, without an EQ. Try doing this with an EQ and often, desirable traits in system, such as detail retrieval and PRAT are lost. Different microphones, placement, recording engineers, studio efforts overall, producers intentions, etc. Any and all variables can combine to make or break overall system presentation.
And for someone who was taught that cables will never make a difference, or if that same person holds this view strongly, then it's true - all cables will sound the same to them. People become believers in cables not because they believe in them so much, but rather they don't have preconceived notions and confirmation bias clouding their judgment when changes are audible.
Soak up the sound like a sponge and enjoy.