People inside the US could trade encryption libraries. They just couldn't send those libraries to outside the US. You could download a cryptography library from outside the US, and your foreign recipient could do the same, and thus send emails back & forth. In practice all it meant was that US developers couldn't write make useful cryptography libraries, and the development got done elsewhere.
The US still restricts the export of (some) cryptography to (some) countries & organizations. Mostly that just requires submitting a self-classification report to the BIS stating that the cryptography is "mass market" and matches the definition thereof in the export regulations.
But what happens if the company you're trading with has non-US entities? Or traveling salesmen?
The issue here is the complexity of complying and closing all loopholes that would allow the government to bring the full weight of the legal system against a library writer.
You're not reading or comprehending the multiple correct replies. I won't repeat them because apparently that won't get through to you, but you should go back and read them again and again until you understand, or at least stop repeating the same incorrect information, if not finally understanding the correct information people keep trying to tell you.
You don't understand the legal liabilities people open themselves to if they provide the software.
Now they have to fully KYC customers to make sure they are from the US, with US only storage, and firewall so that people travelling cannot use the encryption library from out of the US.
You've seen the lawsuits on just P2P link providers, this is even worse.
