## Image

"Why" is a difficult question to answer, generally. But in this case it is really easy to draw a mental picture:

Imagine a complete set of billiard balls nicely ordered in their usual triangle formation. This quite literally corresponds to something that is comparatively cold (i.e., the atoms wriggle around relatively little; obviously they are not standing still like the billiard balls).

Now the game starts, and a good player hits the balls so they are spread out over the whole table. This corresponds to a warmer situation; the wriggling of the atoms increases.

Note that it does not matter how exactly the balls come to rest: *any* configuration of the balls is widely different from the original starting triangle, while there is only *one* starting position. Also, it is *very* easy to create any chaotic configuration of the balls (just hit them with the cue however you like), while it is quite complicated to return them to the triangle configuration if you only can use the same cue to move them around, not the triangle frame.

Now, to relate to your question:

- The balls are the atoms.
- Balls in an ordered state (triangle) correspond to colder atoms.
- Balls in a chaotic state correspond to warmer atoms.
- Electrons correspond to the cue.

## Conclusion/answer

Orderly electrons (currents) randomly hitting atoms easily make those wiggle around more (heat them up); which means it is easy to build an electric heater. 

Heated atoms somehow making electrons moving around in an ordered fashion will not happen spontanously, there will never be an "accidental" current being generated from heat.