Western character designs are typically less detailed because western animation style involves much more movement and action. Simpler designs facilitate this.
Japanese animation favors more complex designs, and cuts down on movement to account for this. Pay attention to how many extended shots in anime are a slow pan with no movement, or how when characters talk their faces/jaws don't move at all. It's because moving the complex character would be too expensive.
So basically anime and cartoons just choose a different area to cut corners in, but both cut corners. Sometimes extremely high budget pieces come out that opt to not follow the style, such as Ghibli or Disney, but these are rare because they are expensive. Also, some shows try to do both, such as Avatar. Avatar was very high motion, a well as high detail, but they still cut corners somewhere, and for them it was the frame rate. Drawing fewer frames allowed them to put more detail into each frame without sacrificing the action of a scene. These Ghibli, Disney, Avatar, and other things like them are exceptions though, the common trend is to just go for detail or action. No one style is objectively better or lazier than the other.