Why is it so hard in many animes to draw people running?
I mean even if the whole anime drawing is good, somehow when someone is running it feels so awkward. Their body movements don't look realistic. Sometimes people seem to be leaping or scrolling. Sometimes their steps seem to be longer than a normal human could walk.
There are exception of course, but they are so rare.
The walk cycle is considered to be one of the most basic aspects of animation.
American animators and animation enthusiasts often times scorn the Japanese styles and methods of animation as lazy, while Japanese anime enthusiasts deride the American style as clunky or too comical.
Why is that you ask? The answer lies in how these countries distribute their budget and time.
While American animation often times may seem lacking in it's attention to detail, it makes up for it the quality of their animation. American animation often times meticulous and original in how they animate motion, though sometimes content is reused cyclically, the animation is painstakingly frame by frame.
In contrast, Japanese anime uses a lot of shortcuts (to save budget and meet deadlines). Typically long scenes feature only the mouth of a character (and maybe other minor features like a waving hair or glittering eyes) moving during delivery of key information/dialog, or the short burst of motion of some character in some an action pose against an animated, cyclic, and stylized background (I'm looking at you transformation scenes). Often times these uses of dramatic still-shots are done against patterned (or static illustrated) backgrounds, sometimes a few moving emotive icons (sweat drops, question marks, small chibi animated heads) will accompany a some sort of monologue. Admittedly both styles of animation reuse shots and sequences, but it's more noticeable in Japanese anime for various reason (e.g., not enough budget and/or manpower). This is why Japanese anime is typically labeled as "lazy" by American animators and enthusiasts.
A typical walk cycle in animation consists of 8 keyframes typically:
The smoothness of an animation is typically determined by the framerate and amount of key frames in the animation.
In American animation, the animation is captured by shooting two frames of film per drawing at a rate of 24 frames per second (fps) to achieve the smooth motion of American animation.
Japanese anime, while it also runs at an average 24 fps, typically captures their animation at a rate of three or four frames per drawing in order to save money and manpower. Though it varies depending on the studio and tools used (e.g 3DCG) with main objects in the foreground (typically characters) are animated at 8 to 12 fps, while background objects can be animated at as low as 6 to 8 fps.
Lets compare the difference between one walk cycle that is 8 frame to one that is 16 frames, both at 60 fps:
<-- 8 frames 
<-- 16 frames
Notice the 16 frame one is smoother, but slower while the 8 frame is faster, but choppier. This is because it takes the 16 frame animation twice as long, covering more frames, to go through one cycle than the 8 frame one.
The varying of frame rates can also be be used to depict the expansion and compression of time (think bullet time from The Matrix). However generally choppy animation is the result of not enough keyframes in your animation. More frames mean more and manpower and/or time, which ultimately means more money is required. Japanese anime production don't typically have as big of a budget compared to American productions (but there are exceptions), so they must make do with what they have and cut corners where they can (like Shaft did with the certain Bakemonogatari TV episodes).
In the creation of Japanese animation, the director creates the storyboards (think of them as scenes) to assign to key animators. I'm mostly unsure where the blame lies, but I theorized that it's mostly on budget and time constraints. The key animators are good are making people run in a 2D plane (x, y dimensions). However, some might find it difficult to do it in a complex perspective assigned by the director. Additionally, the director hands a specific amount of frames that they have to accomplish it in so it won't break the overall timing/flow of next scene. In some instances, the key animator is successful, but the inbetweener makes it appear "off".
It mostly depends on the key animator. Toshiyuki Inoue, Mitsuo Iso, Hideaki Anno, Hiroyuki Okiyura and Shinji Hashimoto were known as "realist" animators. Yoshinari Kandada pioneered the "Kanada" style. It's hard to describe what it exactly is, but it was prevalent in 80's mecha anime and in most Gainax anime. It's described as "spastic", or choppy looking. Despite Eastern animation favoring composition over animation, the fight/action choreography is hailed constantly.
