The account is created on-prem using the new-cshybridapplicationendpoint commandlet found in the Skype for Business On-Prem module. The reason for this is so that during coexistence between Teams and Skype for Business On-Prem both applications need to be able to call and search for the account to access the Call Queue or Auto Attendant.

In fact, when in hybrid Skype Online requires you to create hybrid endpoints and will not permit you to create native cloud resource accounts. Hybrid Application Endpoints allow SfB Hybrid organisations to create resource accounts that can be used for PSTN termination to Cloud Auto Attendants and Call Queues when using Direct Routing. If you do not plan for this, then you can quickly get into a situation that is unmanageable. Before you do however, there are a couple of very important items you need to plan for with specific regards to voice. The time will come very soon when your organisation will be looking to remove Skype for Business having migrated all your voice and collaboration workloads to Microsoft Teams.

Cannot uninstall skype for business