It is? (⊙x⊙;)
Maybe because it would be difficult for the artists to have to design a castle for their story. So most of the creators all use the same structure (perhaps?).
So they're buying the art or is it free?
Some of it
A lot of the times, artists buy stock art that they can use in their comics (usually buildings, objects, cars...etc.). This speeds up their work.
That explained why. That castle must be pretty popular then(⌒▽⌒)
Yeah, some stock art is more popular, than others, so you'll run into them in multiple manhwas and such. :-) Hotel rooms are another example for this. I have seen the same hotel room in like 4 different BLs xD
Why does like every manhwa that I read has the same castle? Like.... why?