Why do earphone wires always get tangled up in pocket? What is the reason? 
Is it caused by their narrow shape, the soft material, walking vibration or something else? 
 A: Because they are too long for the confined space. Reasoning: A very short string can't clot (say 1mm). So it needs a certain length before it can start clotting.
If they could be placed neatly (say big pocket), they wouldn't clot because the ends are too far apart.
They must be flexible. A steel bar doesn't clot.
So you need certain elements to be just right:


*

*Long enough

*Confined space

*Flexible

*Sticky surface (finger/skin oil, soft material, etc).

*Ends must be free to move


In the usual case, the string will be stuffed into the pocket without much consideration, so it will actually start somewhat clotted. If the ends aren't fixed somewhere, they will easily weave with the rest of the string. What makes matters worse is that the ends aren't thin. So you can't untangle everything by simple pulling.
The easiest way to avoid clotting is to fixate the two ends. In my case, I have a clip to pin the volume control to my clothes. If you fixate the two ends with that clip, they don't clot.
