I can't see how having a namespace for each folder makes sense. As near as I can tell, the point of having namespaces is to avoid name conflicts. But, Microsoft, in their namespace naming conventions, says:
❌ DO NOT give the same name to types in namespaces within a single application model. For example, do not add a type named Page to the System.Web.UI.Adapters namespace, because the System.Web.UI namespace already contains a type named Page.
If you're going to follow that recommendation, what is even the point of having more than once namespace per project? Let alone having a new namespace for every folder in a project?