Company groups that are part of the same concern have a really good opportunity to have coordination effects by using a common ERP system. Dynamics 365 Business Central has a number of features that not only distribute costs between several companies but also streamline the daily work of the users in the concern.
Efficient companies are more profitable than others! Efficient in their routines and efficient in their approach to customers. Combining internal efficiency with routines that make it easier for your customers to access information and collaborate with you is a very good combo. Case management + direct access to business data in the company's customer portal is something that not only provides better customer care but also improves internal efficiency.