That's an interesting way to look at it.
Knowing biology would mean that it would be better to expose a lifeform to as many strains of an infection as possible, as to build up their immune system, not to tear it down by underutilizing the immune system. But hey... what do I know...
I am not sitting here saying "Hey, lets kill a bunch of fish!! Sounds like fun!!!" What I'm saying is that
I would prefer my tank, pets, family, etc have immune systems as ready for anything as possible. I have read that this may be a reason that greater Apes pick their nose and eat it, as this is a safer way of introducing various pathogens to the immune system, especially airborne pathogens.
While one or two people may have the perfect QT system and are able to follow it to a 'T', even then they can introduce an unknown pathogen to their systems. It just so happens that this pathogen is carried by a fish or invert that has the proper antibodies to fight it, introduce this fish and the rest of your tank has no antibodies to defend against the pathogen, and poof you have a bunch of sick and dying fish.
When this happened to me ~10 years ago with a fresh water tank that I never let anything in without proper QT, and by proper I do mean proper, 50-90 days in QT, Metronidazole, erythromycin, Praziquantel, ich-x, etc... Running the tank through these cycles multiple times, doing everything in my power to not introduce anything unhealthy, sickly, or possibly carrying anything bad to my tank. Added these fish to my tank, and a couple days later... entire tank (save for the added fish) are sick, and start dying off.... It happened very rapidly, and I didn't have time to catch it. It was through this experience that I came to my current beliefs.
We each have our own experiences, and I respect yours. However mine doesn't jibe. From my standpoint, you can do what you want, do what you feel is best, more power to you.