The big question is can you live without kidney? I guess the answer is NO so therefore Bitcoin is the kidney of digital currencies.
It makes more sense that you can't live without a heart, while you can still live without a kidney. Then why the kidneys, not the heart?
It's hard to make an analogy if you don't have enough knowledge about the subject yeah I agree it should be the heart because you can still function without kidneys through dialysis, and this is the first time I stumble comparing Bitcoin to kidneys when the brain and hearts are the most essential part of the body.
Anyway, this is all about Bitcoin as the king of Cryptocurrency this is what OP is trying to say and we can all agree.