With server-side encryption, the cloud provider controls they key. This means an administrator or disgruntled employee can access your data, or a simple misconfiguration could make your data publicly available. If car keys were stored in cars, there would be many more car thefts.
Much like trying to find a key phrase in a textbook, an index is necessary to find the correct encrypted file blocks in a cloud storage system. Oblivious creates an index entry for every file uploaded, encrypts this index, and then uses a neat math trick to find it again. The server needs to store the encrypted index in order to search for it later.
Oblivious is for enterprises and application developers that use or want to use cloud storage while maintaining data security. Life-sciences and healthcare companies are required to keep PII data secure. Automotive and aerospace firms spend millions on research and development and a breach could have immeasurable cost. Financial institutions have many legal and compliance obligations for customer data security.