There are other approaches on how to provide confidentiality and verifiability, where the most famous are probably zero-knowledge-proofs. However, there are always trade-offs. As an example, zero-knowledge proofs do not scale at all with the current technology. We claim that it will take years for the technology to evolve to be performant enough for many business cases.
From a security perspective, however, TEEs are the only solution providing an additional security layer to prevent attacks with system admin privileges. Not even the OS, nor the system admin, can read and execute data within a TEE. The last open question here would be: Why SGX and not other TEE technologies? Here the answer is simple; only Intel SGX currently provides remote attestation. As soon as other technologies become available, we will consider incorporating them into our repertoire.