Actually I have rarely seen it referred to as a "charge". "Margin" certainly isn't a "charge".
But when looking at a stock like ANDI, if someone was able to find enough stock to borrow to make say $1000 AT MOST if the ticker dropped to 0.0001 they would need to put up $250,000 in margin (ALL at risk).
That type of risk makes no sense on ANY level.
And that margin requirement is the primary reason why penny stocks are rarely shorted.