I am truly angered by this post. You are viewing the matter solely as a skeptical and scientific person, not as a drummer. The supraphonic snare drum is the most recorded snare drum around for a reason. You claim that the reason is that only a few producers were working back in the day, and they just so happened to be using supras. Tell me this. If they didn't enjoy that drum, then why would they continue to use it? If a better drum was readily available to the public, then producers would be apt to get their hands on it.
As previously stated, many drummers used the supraphonic as a personal drum because of personal preference. I don't know 'em all, but I know a few off of the top of my head. John Bonham, Mitch Mitchell, Keith Moon, Nicko McBrain, Steve Gadd, Phil Collins, Ginger Baker, etc. I know that there are more, I just can't think of them right now. Regardless of whether or not some of these drummers used other snares alongside the supraphonic, the fact still stands that the supra was part of their arsenal, and there was a reason for it.
I also noticed that you said that the supra doesn't sound like the best drum around "to your ears". That fact is irrelevant. Guess what, the supra won't sound like the best drum to a lot of people's ears. It's personal preference. To my ears, the 14 X 6.5 MCX snare from Pearl sounds the best. When listening to a drum, you should pay attention to its overall response. Is it sensitive? Is it versatile? Is it resonant? Does it have a nice pop? Is the hardware easily maintainable? Is it dynamic? These are all properties that the supraphonic smashes. It is known as the best snare drum to have ever been made because of its outstanding overall performance in comparison to other snare drums.