Why are digital streaming equipment manufacturers refusing to answer me?

I have performed double blind tests with the most highly regarded brands of streamers and some hifi switches. None have made any difference to my system on files saved locally. I have asked the following question to the makers of such systems and almost all have responded with marketing nonsense. 
My system uses fiber optic cables. These go all the way to the dac (MSB). Thus no emi or rfi is arriving at the dac. On top of this, MSB allows me to check if I receive bit perfection files or not. I do. 
So I claim that: if your dac receives a bit perfect signal and it is connected via fiber optic, anything prior to the conversion to fiber optic (streamers, switches, their power supplies, cables etc) make absolutely no difference. Your signal can’t be improved by any of these expensive pieces of equipment. 
If anyone can help explain why this is incorrect I would greatly appreciate it. Dac makers mostly agree, makers of streamers have told me scientific things such as “our other customers can hear the difference” (after extensive double blind testing has resulted to no difference being perceived) and my favorite “bit perfect doesn’t exist, when you hear our equipment tou forget about electronics and love the music”!
One reason might be that the distributor knows nothing, because some company like Foxconn designed and built it, and sells it to them to market.  Have you ever wondered why so many companies' televisions have stick on brand names.
It is not just electronics, either.  The new Supra is said to be made by BMW.  It is not, and neither is that BMW.  An Austrian company that designs and makes about 200,000 cars per year makes both, as well as the Mercedes G series, and others.  Like Foxconn with electronics, they design and make stuff, then sell it to other companies to provide drive trains, and then to market.  You can verify this by entering the VIN into your computer.  Also, the Toyota Sports car, that is the same car as the Subaru, has a VIN beginning with JF, for Subaru's  parent company, FUJI. 
German built cars built by BMW begin with WB.   W is for West, as in West "Germany".   Mercedes is WD (Daimler).  For vehicles made under contract for Mercedes,  ZA and KN are used.  If it starts with a J it is made in Japan, with numbers 1-5 in North America (USA 1-3).  The first letter of number is the country code. Who know who makes what anymore?
The Supra was designed by Toyota, using a bevy of BMW parts from the Z4, and ASSEMBLED by Magna Steyr. This is a contract manufacturing model that probably applies at least at some level, to much of the electronics industry at some level. Even Apple does not see value in setting up their own manufacturing lines.

That is much different from the model you are using with Foxconn where Foxconn sells it for rebadging. This is not contract manufacturing it is ODM (original design manufacturing). It does apply to some televisions, usually lower end models like Magnavox, RCA, etc., and perhaps some low-mid end models in other manufacturers, like Philips, but not to most of what you buy from say Samsung, LG, Panasonic.

I am not aware of any streamers in the audiophile world that would fall into the ODM category. That would be low end offshore DACs.
Jmphotography, in the system you describe there is no fiber optic blocking all noise and as a result I completely understand that there could be improvement with a good streamer. Thank you for that feedback.
Given the light discussion around ab(x) testing, as a scientist with phd training in human data collection and cognitive functioning, I object to the (x) part of the judgment task.

Identification should not be the goal. We listen to equipment to decide which we prefer... which is better.  That should be the decision when doing (blind) ab testing.

If I were designing the test for audio equipment, I'd let people switch back and forth as many times as they like, taking as long as they like for each (level matched) sample.  Eventually they just decide which they like best. Repeat that task over and over throughout the course of listening to music and I guarantee that people will begin to find their true preference and that that preference will be consistent. 

It's very easy for the brain to develop and make decisions based on good/bad/preference and much harder to make the decision based on label identification. They are different processes in the brain and preference is the more basic, a primary system. Newborns know what they like and what they don't and will often show good a/b consistency. The brain doesn't even need to identify a stimulus to make this judgment. That comes later because it's less important. First, figure out if something's good or bad, then if you've got time, figure out what it is.  This is the order of processing for all of us.

The eye doctor uses this ab-preference testing when they're figuring out your prescription. They flip between two possible magnification factors and you just tell them which is better. It works great for letting you find your own way to an optimal solution. They don't care about labels or giving you mystery options and having you say whether it corresponds to a or b because that's irrelevant. It would make the process less effective. 

And finally, I'll just say that if you don't believe in blind testing, you're lying to yourself. There's decades of research demonstrating the impossibility of avoiding the biasing effects of pre-existing knowledge. People have used samples of scientists trained in this area of research and they are just as influenced as you or I. You are not immune.

That said, it's hard as hell to do blind testing and I never do. Fortunately placebo effects are very real and they help your preconceived decisions feel right even if they were wrong.
If you were a PhD with said qualifications, you would know the X has nothing to do with identification, it is to test reliability. If you can't match A or B to X, then you can't tell the two apart and you hence have no preference as you don't as actually prefer either.

Given the light discussion around ab(x) testing, as a scientist with phd training in human data collection and cognitive functioning, I object to the (x) part of the judgment task.

Identification should not be the goal. We listen to equipment to decide which we prefer... which is better. That should be the decision when doing (blind) ab testing.