BriskBard, CEF4Delphi, WebView4Delphi, WebUI4Delphi and WebUI4CSharp

Probably a stupid question( But what is the point of using subprocess?

For example, this will reduce the load on the main form of the program, since if many browser instances are created and the form sometimes freezes when browsers are active.

Or in which cases is this option even necessary or desirable?

There're several reasons to use a different EXE for the subprocesses.

Some applications have a complex initialization. They have code in the initialization section of their units, linked DLLs, etc. Some of them use mutexes to check if there's only one instance of the application running.

In other cases the developers are not allowed to modify the DPR file in any way.

Some other projects need to embed a browser with a plugin or in a DLL.

I'm sure there are more reasons but these are the most common I've heard.