The creators of the show DB & DB are making it up as they go along, they have been radically been altering the show lately from the book in events, timelines, and screen time to move the show in a different direction and to an ultimately different timeline.

Part of this is just a translation from book to show, part of this is that only got about 70 episodes to film and actually finish the series while GRRM has 2 more (maybe even more) books to write and it is doubtful he can get them done in the 2 years needed for the show to follow the books faithfully.

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This doesn't mean things are bad necessary when you are spontaneously making it up as you go along...the hound's line about "a man gotta have a a code" was well done and it was not in the books.

Yet things like you mention are common when you are making it up as you go along. It has to do with time and deadlines, and only having so many goes at it. George RR Martin (now as a book writer) by contrast is a perfectionist, and he won't release a work until he feels it is right and the quality of his work is shown by his relentless perfectionism.

Think of it as a difference between a cook who is told to spontaneously create a recipe, with only the ingredients in a kitchen he is not familiar with, and he has to be ready to serve in 90 mins. Compare that to a chef in a 5 star restaurant, a man who has to work on the product for months or years until it is just right, followed by him showing it to the public in some artistic presentation.