West Germany officially embraced the myth with the Himmerod Memorandum in 1950, and America, at the time led by President Eisenhower, signed onto this in support of their Cold War ally. It wasn't until 1995 that Wehrmachtsausstellung thoroughly assembled and showcased evidence disproving this myth. By this time the myth had been around for 45 years as the dominant narrative surrounding the Wehrmacht, it had become ingrained in pop history, and most people were genuinely unaware of how false it was. While it may have been dealt a serious blow in academia, it takes a lot longer for a myth to be completely dispelled. I see it repeated all the time by history buffs earnestly hoping to share their knowledge, they aren't nazis or even using it as part of some agenda, it has just become a huge part of what is presumed common knowledge. That is not to say everyone who repeats it has earnest intentions, it plays a large part of Nazi apologia. A good comparison would be the Lost Cause myth of the confederacy, it has been taught for generations despite the huge distortion of history that it requires.

Ultimately for a variety of social and political reasons, people cling to this myth and perpetuate it. I think you vastly underestimate how quickly academic discourse actually permeates mainstream culture. A single popular movie or tv show would probably have far stronger an effect in actually bringing the inaccuracies to light for the general public. Elements of the myth were included in my high school history classes and that was well after it had already been academically exposed. Combine the political and cultural incentive the myth provides to its supporters with the lack of resources the general public is exposed to that would actually counter this myth and I wouldn't be surprised if this myth stays around for another few generations.