There are a few legal reasons: there is a difference in the expectation of privacy when you never actually hand the plaintext message to the server. This is the

There are a few legal reasons: there is a difference in the expectation of privacy when you never actually hand the plaintext message to the server. This is the logical equivalent of a the difference between letter mail and a telegraph. With a telegraph you have no expectation of privacy and therefore no legal right to keep that information secret as opposed to your letter mail. Furthermore, the government cant legally force a company to not insert a backdoor but crack their own security (at least as of yet). The latter statement meaning that it cant force a security company to hack their customers to get their keys. I think that while these dont result from any specific crypto issue, they are very real legal issues.