Query on promotion management in BI 4.0

Hello Experts,

Currently we are following below workflow while transporting the content between the Dev->Quality->PROD  using Promotion Management in BI 4.0

We want to known What is benefit of using the dedicated Promotion Management System in BI 4.0 as shown below  and what will be impact if we not implemented.

Is it require to install the Version Management in  each system like DEV,QAS ,PROD  and  dedicated system.Installing the VM only in dedicated system is not sufficient?

Thanks in advance

Regards,

Vinay