The other thing being that nobody makes these absurdly "sandboxy" open worlds that Bethesda does. Games like The Witcher 3 or Breath of The Wild are great games, but they don't compete in the same space as Skyrim.
More or less why also Bethesda keeps reheating their ancient engine. Games are unstable, buggy and technologically behind, but they sell like bread.
Meanwhile, Telltale's got good competition from games like Life is Strange, or some other story-driven point-and-click games I know exist but can't research right now.