Original MVC architecture
In the original MVC architecture (Xerox PARC in 1979), the controller handles the user interaction. It interacts with the model and with one or several views. The split of responsibility requires that the controller doesn't intervene in the rendering which is of responsibility of the view.
In this architecture, there is no need for services : it's perfectly valid for a controller to access domain objects directly.
This is different from a MVP architecture (initially introduced by Talligent in 1996), where the presenter (aka controller) acts as middleman between the view and the model. The idea is that in a client-server architecture, the presenter could be split between the the server where the domain model is maintained, and the client that takes care of the view.
This is why, in MVP, the controller is supposed to only access the model through "commands" and "selections". So here a service layer should be used.
Service layer or not ?
This article makes the difference between MVC, MVP and MVVM clear.
Unfortunately frameworks often have their own understanding of MVC (e.g. Apple or Google Chrome team). It's not clear which MVC framework you are using : if needed edit your question to clarify.
Nevertheless, regardless of MVC, a domain could be supposed to be used by several application via an API (or implemented as a microservice). Then a service layer could be required because of other architectural considerations, and not because of MVC.