Distributed systems containing several applications certainly need more organizational effort than a single one.

Multiple applications imply multiple deployments that need to be managed. Deploying new versions may have an impact on dependent applications. Teams need to ensure that versions of deployed applications work together well. Single, monolithic applications are not affected by this since they are consistent within themselves.

Besides that, multiple applications are developed in several projects and repositories, usually by multiple development teams. In particular, having multiple teams requires communication, not necessarily technically, but human-related communication. In the same way as for deploying applications, responsibilities, system boundaries, and dependencies need to be agreed upon.