That's true. (Commentaries on the Laws of England summarises a tradition older than the United States, but your point still holds.) Maybe falsely imprisoning innocents en-masse is okay, provided that (for example) the false imprisonment ratio is low enough and it could not easily be lowered further.

But it being okay isn't the same as it not happening. I'm not sure why you asserted that it doesn't happen, when it's a well-known problem. See, for example, https://en.wikipedia.org/wiki/Kids_for_cash_scandal (2003–2008), though it's rarely that blatant.