It is misinformative for you to state that as though it is a universal property of all LCD panels. It probably was as recently as two or three years ago, but it certainly is not anymore.
Perhaps it has been a few years since you have visited an electronics store. Two or three years ago, the effect was time smear, which was due to the decay time or hysteresis being too slow. That was fixed, as evidenced by the fact that many of LCDs from a year or two back exhibited a jerky effect with motion. There is no way that the jerky effect could occur as long as the hysteresis was too great (slow). With the hysteresis problem being fixed, all that was needed to fix the jerky effect, which was effectively due to the over-correction of the hysteresis problem, was to double the frame refresh rate. If you do that by synthesizing a complete (progressive) frame in between each time-adjacent pair of complete frames in the signal, then there can hardly be any doubt that the net effect will be an improvement in the perceived smoothness of the motion.
It should also be noted that when reverse 3:2 pulldown is applied to extract 24 original frames per second for content that was originally shot at 24 frames per second, that the ratio of original frames to frames as presented on the screen is a nice integer ratio of 1:5, which tells you that in between each time-adjacent pair of original cinematic frames, you need to synthesize four frames. Were you to simply repeat each frame four times, the effect would be very similar to the jerky motion that you see in the theater. If you have observed jerky motion with an LCD panel TV that uses a screen refresh rate of 120 Hz, the most likely explanation is that you were watching film-based content where the LCD TV had applied reverse 3:2 pulldown to extract the original 24 frames per second, but then simply repeated each frame four times in succession. If so, what you saw was very much the same as you would have seen had you watched that film-based content in a theater.
