Why don't cheap toy robotic arms like [this][1] move smoothly? Why can't it even move itself smoothly, (even without any load)?

In other words - what do real industrial robotic arms have, that cheap toys don't? [1]: https://www.youtube.com/watch?v=4xP9OtcGpUk

Why don't cheap toy robotic arms like this move smoothly? Why can't it even move itself smoothly, (even without any load)?

In other words - what do real industrial robotic arms have, that cheap toys don't?

Why cheap toy robotic arm like [this][1] does not move smoothly? Why that toys can't even move itself smoothly - I'm not even considering adding some load.

In other words - what real industrial robotic arms have, cheap toys don't? [1]: https://www.youtube.com/watch?v=4xP9OtcGpUk

Why don't cheap toy robotic arms like [this][1] move smoothly? Why can't it even move itself smoothly, (even without any load)?

In other words - what do real industrial robotic arms have, that cheap toys don't? [1]: https://www.youtube.com/watch?v=4xP9OtcGpUk