The main use case is "systems integration" for my company's enterprise customers across many different industry sectors.
One of our customer projects that use Oracle Integration Cloud or OIC iPaaS is ERP to e-commerce integration. Integration flows were developed for keeping product inventory, prices, addresses in sync between various end-systems. Additional non-functional goals were maintainability, stability, scalability, graceful error-handling, and "predictable performance". The predictability has been verified via repeatable testing and seamless operation in production.
Additionally, we have implemented other use-cases like shipping integration (such as DHL, FedEx), order flows from e-commerce to ERP, & many more granular and custom use cases specific to customer needs (e.g. implementing internal APIs to support larger enterprise business processes or application user interfaces, bulk data reconciliation and many more).
In general, a cloud-based product helps avoid the high lead-up times and maintenance overheads involved in setting up in-house infrastructure, and this is adequately achieved by OIC iPaaS.
OIC, in particular, is also well integrated with Oracle SaaS ERP via "business events" and easy to integrate via Rest APIs (though other integration platforms also offer API-based integration, it makes a lot of sense to use OIC if a customer already uses Oracle SaaS).
OIC offers a number of pre-built technology and SaaS adapters for high productivity for a wide range of target systems, both in-house via agents and cloud/SaaS, via a very flexible range of interfaces. These include APIs by way of Rest/SOAP over http/s, files like ZIP and CSV over filesystem or S/FTP, databases, and more. All of these interface types were utilized in our customer solutions to deliver a range of functionality in the form of "integration flows".