Don't get me wrong, they are better than nothing, but from what I understand, it's really simple to abuse them to either promote/slander a vendor dishonestly with EC test results. Not to mention, even if they are real, they are only indicative of one order and we all know product quality can fluctuate wildly.
I'm not bashing EC or anything, I'm just asking why so much weight is put on them, as if that one result is and end-all-be-all indication of a vendor's product.
Because it's one of the few ways - if not only way - to quantify quality. Reagent tests only indicate the presence of a substance; not how much or what else there is.
Gas chromatography machines are expensive. Even rarer are organizations willing use theirs to test drugs for the public for a nominal fee.
TL;DR It's the best we've got.