I honestly don't think the patent office can draw the right line on what mathematical formulas are discovered vs invented, so that seems reasonable to me.

I think you are looking at the abolition of patents from a very "software" perspective. Copyleft license terms have basically never been tested in court, and could just be unenforceable, but the tradition of software engineering seems to keep the peace there - GPL'ed and other open source hardware (which frequently has copyleft licensing) frequently gets ripped off without credit and nobody does anything about it. These would have bad facts in a court case, since the copyright doesn't cover the thing, just the schematics.

Trade secrets also generally don't protect you when your product is easy to reverse-engineer and you have customers or competitors with a lot of money to do it. A drug is a prime example of this.