Blind listening tests are not the ultimate, definitive final answer to which products are better.
They're just the best and the most scientific means we have of comparing the sound signatures of different products.
It has been long established that the human mind is subject to a great number of biases and preconceptions when it comes to forming judgements.
Sometimes these biases and preconceptions can be helpful eg if you see a growling dog approach you with its fangs bared, you don't need to think very hard before taking evasive action etc.
Other times they may not be so useful, eg a 50k amp MUST be better than a 1k one.
Therefore since most of these biases are closely linked to sight, it makes good sense to break that link in the first instance when you are looking solely at sound quality, does it not?
Blind listening tests are not perfect, nor were they ever claimed as such.
However, in comparison to sighted listening tests, there is simply no comparison if you what you want is a judgement based primarily upon sound quality.
For me, even the simplest blind listening test is vastly superior to any sighted one. Most of the times I've done one, I've been surprised at the results.