One possibly positive result does not outweigh the hundreds (thousands?) of times it has been tried and nothing much has happened. The Chinese government, for example is enamoured with it and does it a lot, with no particular positive results to show for it. They tried to make it snow when they hosted the Winter Olympics and got nothing, to pick one random example.
As I said, the evidence for it is very very weak, and all the markers of pseudoscience are here.
When it has appeared to work, nobody has succeeded in showing that it wouldn’t have rained anyway if they had done nothing.
