Because some people have been harmed by it. It's different for everyone and hard to know what will work for who. If you got better on that alone, then your system is obviously working right and is able to eliminate the mercury with the help of NDF. Other people have problems, so that the mobilised mercury can make them much worse.

One girl took NDF and was almost bedridden for two years (as far as I know, she is still not coming right).
Although my view on this is, she may have had a stored load of mercury and the NDF may have erupted it, or pushed the storage into offloading into her blood, as this can happen even on its own sometimes, or it can take something to start it off.

But at any rate, there is risks attached to many chelation therapies and so very hard to know what will work for everyone. I only know one that cuts down the risks of mobilising mercury and concentrates more on removing it and many are on that and improving (protocol by Andrew Hall Cutler (biochemist).

NDF may be just right for you and is obviously doing the job. You should stick to it. I have tried it and had varying things occur, I am in no hurry to try it again, but I am in a bad conditioin with other issues as well as mercury (which might be why).

There are some people who seem to perpetually struggle and remain somehow unwell, others seem to heal and get on with their lives. I assume that those who remain unwell have multiple problems, not just mercury. Those who are poisoned and ill, but mercury is the main issue, can seem to come right over time with detox.