Its actually the case that we always need to install a orchestrator in a server only There are many reasons on installing a orchestrator in a server
When you need more control over the environment, as your RPA needs grow, you can easily add more robots and workflows to Orchestrator without having to worry about performance or capacity constraints.
When you have a large number of robots reason being a server has more resources than a typical computer, so it can handle the load of managing a large number of robots and workflows.
In all the UiPath projects that I have created, I have never had to do this installation, I only publish my projects and manage them from the orchestrator in the cloud.
it depends
if you are using cloud orchestrator then the cloud-based version of Orchestrator is hosted by UiPath and takes care of all the infrastructure requirements, including routing. This means that you can focus on developing and deploying your RPA projects without having to worry about the underlying infrastructure.
you need to install only if its a On Prem orchestrator where it has to be hosted with a server