1. If we talk about "core" , actually it represents application ,where application composed of several components, which are packed in bundle.
Our project specific complex business logics are part of this bundle.
2. We could see out of the box OSGi configurations and these are playing crucial role in terms of maintainability, establishing connection with DB, LDAP, SAML (just imagine you can update property file during runtime)
3. An increasing number of open source projects, provide their jars are ready for OSGi. This helps in re-usage of available technologies and functionalities.