Water Culture or Vase Culture

[Arizona Jeanie]

Hello all,
When I first started learning about proper care of Phalaenopsis, I read a great deal about how to prevent root rot. That seems to be a common cause of their demise, so I carefully potted in a coarse bark mix, let them get quite dry before watering, and repotted into fresh mix when the old stuff started breaking down. My plants have done well, roots are healthy and without rot, and they've bloomed every year since.
So, after all of the above, I was astounded to read about full water culture or vase culture--whatever you want to call it. I had to try it right away, stuck a NOID phal in a quart mason jar, and waited for it to die from those roots being not only wet, but in water much of the time. That was a year and a half ago, and the plant is going strong. I had to move it to a bigger vase to hold all the roots, and it's just starting to spike again. Three new leaves this summer. It looks just as happy and healthy as the plants in bark.
My question for you-all is this: why are roots in media so prone to rotting if they're kept too wet, yet the plants thrive when the roots are constantly wet in a vase?