Phanjam wrote
I would like to know what are the advantages of using namespaces in the first place (there must be many good reasons behind their creation, after all)?
There are not necessarily "many good reasons" for namespaces. The main reason is to give your wiki a *structure* (but that depends, it might not need any structure).
Phanjam wrote
Are there things you can do, conveniences you can offer, plug-ins you can use, only if you've used namespaces to structure your wiki? In short, is my wiki "losing out" on something good, if it doesn't use namespaces?
There are lots of things you can do with namespaces, especially with lots of plugins. Just look at
plugins tagged with "namespace" or
a search for the word 'namespace' in the plugin namespace for lots of examples.
But if you're really "losing out" or not, again, depends on your use case.