I agree that if you can get lucid dreams from a good nights rest, then there's no need for devices or medicines.
But thats not always so clear cut.

EG
1) If you CAN'T seem to get lucid at all... then what?
2) What if you have sleeping disorders and can't get a good nights sleep. Then certain natural drugs might be necessary. Eg. Melatonin.
As it is Melatonin sounds like a miracle drug.

Yeah I know : 'If it sounds too good to be true.. blah blah'

BTW, if anyone is curious a good site for Melatonin info is http://www.melatonin.com/melatonin-faq.htm#SIDE