I don't think anything. I KNOW

that it is a limitation caused by the frame rate of the original film. I don't know if US tv's has this, but in Europe Philips has tv's with a feature called Digital Natural Motion on some 100 Hz tv's. This feature interpolates each field instead of just repeating them, creating 100 individually different interlaced fields per second. While this causes some digital artifacts (some will say heavy artifacts), it smooths out the picture to an incredible degree. Once you're used to it, anything else is stuttering, including the cinema. I personally notice it every time I go to the cinema, and every time I watch something without DNM. And since I don't own a DNM set, this is quite bothering... 24 fps simply isn't enough to create smooth pans. Personally I think a higher frame rate of the 70 mm shootings is the next step in increasing PQ, but this of course requires heavy investments of the cinemas...
But, in theory, wouldn't it be possible to shoot films in 120 fps? Then you could down-convert to 24 fps if necessary, without loosing anything compared to shooting 24fps in the first place, AND convert to 60P without 2-3 pulldown, resulting in a better PQ than with 24 fps originally.
Could anyone tell me, when HDTV is shot at 720P, is it really shot in 60 hertz progressive, or 30 hertz and then repeating each frame? How about HD D-vhs and stuff, do they contain 60P or 30P?