Germany alone has a dozen "major" dialects which are only mutallymutually understandable for speakers of adjacent regions. Austria and the German speaking part of Switzerland only extend this problem.
It exists sincehas existed for at least the past 1000 years and won't go away. Even though Luther and the Grimm Brothers did their best in the manifestation of a common German language. Also, there ishas been much trade and people moving around Germany sincefor at least the past 200 years. Especially miners and early industrial workers from poor southeast Germany brought their upper German dialects to the industrial regions of northern and western Germany. In that process the dutchDutch-alike PlattdüütschPlattdüütsch variety of German nearly died out while the upper German dialects stick around and new mixed dialects in the north arisedarose.
And that's why German speakers have to settle on a common standard when speaking or writing to unknown people. There are just too many dialects and you limit your audience greatly if you speak/write dialect to an unknown public.