4k video? Holy shit.
First world problems much?
First - world don't seem to have much problems. Though second and and third-world will suffer. 40GB for ~110 minute movie.

Also, like kita said monitor's are professional use and TV's are more for causal use.
Monitors - The color gamut is given more importance and mostly still images are used on it. 4K monitors have been in use mainly in security (their surveillance and stuff) before you even heard of them going commercial.
TV's - More importance is given to the fact it has to display constantly moving objects (the 100hz, 200hz, 400hz etc. motion flow thingy) rather than exact color reproduction.(well, Sony's Triluminous TV's, which include all 4K TV's, actually fixes this problem, that's the reason I have been drooling to get one). And their usage is well less than a monitor aka less life span on average.
TV's also need to be produced in large sizes, 46, 55, 65 inch etc. This actually is hell lot difficult to produce than smaller monitors due to larger error rate in the production of pixels. Not to mention the components, mainly capacitors required, have to be of higher rating to power those large pictures effectively.
So in terms of production itself, Monitors and TV's are totally different, but in normal usage they are different. Sure you can use one for another and be completely satisfied by it, but both have their own specific purpose in which they will excel in general.