Just piles and piles and piles of work. Imagine all the trees, grass, rocks, terrain, buildings, props - and then character and creature models, animations, sounds, writing it goes on and on!
And the simulation complexity, which leads to an endless sea of bugs. Imitators typically just leave a lot of this out. But Bethesda knows that when the player dumps 500 wheels of cheese in their house in Whiterun, they better still be there and fully physics-enabled when they come back 20 hours later.
Just piles and piles and piles of work. Imagine all the trees, grass, rocks, terrain, buildings, props - and then character and creature models, animations, sounds, writing it goes on and on!
And the simulation complexity, which leads to an endless sea of bugs. Imitators typically just leave a lot of this out. But Bethesda knows that when the player dumps 500 wheels of cheese in their house in Whiterun, they better still be there and fully physics-enabled when they come back 20 hours later.