Why are the processors so small?

I will not lie, I was pushed to write the topic of this Q & A. The question I also once thought about.
I will briefly describe why all the same modern processors are so small:
UPD. Comments, as often happens on Habré, came out even more interesting than the topic. I advise.

The first thing that comes to mind is mobile systems. A survey of friends showed that most of them believe that the decrease in the processor is caused by mobile phones, laptops and others. But why, then, in the servers, the processors are not half-board?
The second is the saving of material - the opinion of my humanities friend. By the way, he is partially right.
To the main question, we are kindly answered by holyorb2 (italics - my explanation):

• A smaller tech process makes smaller parts inside the processor. Here it is necessary to explain what the twist of the small parts is: the switching speed of the transistors increases due to an increase in the so-called activity current
• Less energy consumption. Here the question is not so much “pitiful energy”, but the problem of removing such an enormous amount of heat from a small piece of silicon. Let me explain: less voltage = less heat. It is quite logical that it is more difficult to remove 5 kJ from a small piece than from a large one, but it is easier to move 2 kJ from 65nm to 5kJ from 90nm. I exaggerate a bit to convey the main message.
• And one of the most important observations from CKOPOBAPKuH : and yet, at a clock frequency of 3 GHz, the light (and electromagnetic interaction) has time to spread to a distance of 10 centimeters.
  but since the interaction propagates through the processor not directly, but along complex trajectories, the maximum allowable size of the processor will not be 70x70 mm, but smaller.
  The size, for example, of the Xeon is 42.5mm x 45mm. it's in the case. The size of the chip itself is approximately 16x16mm. and this is practically the limit.

Actually, these are the main reasons. In addition to them, I can also point out a lowering of rejection on a finer process technology, which also plays an important role.
I hope you were interested in this little article.
And her goal is cool information about what few people thought about and raising the karma of guys like CKOPOBAPKuH and holyorb2 . Habrachelovek, do not skuspis, guys deserve it.

Upd.2 Do not think for arrogance, but I can not be silent: I very much ask for the vladson habrachelek - he left a sensible comment on Q & A, which I bypassed and during personal communication promised to publish a post on a similar subject - deeper and very interesting. In addition, I can not help but notice that even if his karma is low, he now spends a lot of time on Q & A and comments to get back. Thanks in advance :)