SGX has simply just been shown to be incompatible with secure software and is impossible to justify. Signal can happily operate without the need for this sort of thing to begin with, but they keep insisting on weak solutions for no reason.

These weak solutions are actually enough to keep the government requests at bay, for the moment. Why go into crazy crypto theory if that's good enough right? That's what Apple and Google are doing as well.

As far as I understand, Apple is using dedicated secure enclave chips in their iCloud keychain service; the attacks against SGX are usually (admittedly, not always) side channel attacks due to being able to use the CPU for arbitrary insecure execution and then use that to extract information from the container. It is also my understanding that Apple controlled the keys for their hardware, and could watch themselves destroy the key: as far as they know, they can't access the data themselves and nor can anyone else... Intel SGX is subject to upgrade keys from Intel and their remote attestation can be forced by Intel: if a government wants the data they should bring the computer to Intel and start a similar battle to the one the FBI had with Apple on their older phones (where Apple already had a back door but didn't want to be forced to use it by signing a firmware to access the phone).