Why GitLab uses service objects?

GitLab source code is pretty clear and beautiful to me, In presenters folder there is a detailed guide on why GitLab uses presenters for models, it would be nice to know the mindset of the community on the service objects.

Most of the time they are one-to-one to resource actions, I have experiences with these service objects, the main benefit of these approach for me, has been encapsulating a procedural behavior into an standalone object which may be reused somewhere else in the feature.