Part of the problem historically (into the 2010s) was that MIT had a patent on doses of melatonin under 1mg[1]. So manufacturers could only avoid the patent by

Part of the problem historically (into the 2010s) was that MIT had a patent on doses of melatonin under 1mg[1]. So manufacturers could only avoid the patent by selling larger doses. That patent is expired but to some extent customers probably still think more is better. Personally, I use a fairly large dose of melatonin daily without ill effect; and it works better for me than smaller doses. [1]: https://patents.google.com/patent/US5641801A/en https://patents.google.com/patent/US5641801A/en