Any reason not to use namespace for scripts for asset store

I noticed that some asset store packages name their assets like this company or project name _ then a class name (like vp_Something). This might be to find the classes from a specific asset faster and to know which classes belong to which asset while typing. But this can be also done with namespaces. Is there any reason to do this instead of CompanyName.ProjectName.ClassName. Also is there any document that defines the default way you should name classes and namespaces for unity asset store?