Ever tried to link to a tag-archive with more than one tag?
From a SEO-perspective you might want to optimize keyphrases that constists of
more than one tag you already have in use.
E.g. you have tagged your content with e.g. “piraten” and “playmobil”.
Now you want to see all posts which contain both tags AND you want
to search-optimize the keyphrase “playmobil piraten”
That is, the keyphrase should be in the title and in the meta-keywords and