"Supplements" are a category of drug created for the sole purpose of getting around the safety and effectiveness requirements for drug approval. Let that sink in a while.
Also, they are so poorly regulated that the resemblance between the ingredients listed on the label and what's actually in the product might as well be entirely coincidental.
Some people have conditions that require supplementation for particular vitamins, etc. Otherwise, this whole field is dominated by people who have been masters at selling cheap basically useless crap at high prices.