If you are using the cloud only version of Dynamics 365 for Finance and Operations, Enterprise edition, then in order to perform any activity on production environment, you need to with Microsoft as they are the owner of the environment and you won't have any access to the production environment other than the URL for your solution.
Any interaction with the production environment can be done with a Microsoft service engineer. Hence, any communication with a Dynamics Service Engineer (DSE) needs to tracked, organized, and be user-friendly. Thus, there is a need for a service request so that the customer, partners, advisors, and implementation teams can raise a request for any service needs in the production environment.
Following visual shows the three types of request which can be initiated in LCS as a service request:
The preceding screenshot shows the fly-out when a user clicks on the Add button in the Work items screen under the Service requests...