system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:Why are we spending so many resources to lower transistor size in microchips? Why not just increase chip size to fit more transistors since silicon is so cheap?

I don't get why instead of pouring money and research into making microchip transistors and components smaller, you would just make the chip itself bigger to fit more components? 

Take a computer for example, the size of the processor is extremely small considering it's the heart of the machine and compared to the size of other hardware like hard drives. 

Plus from what I understand Silicon is very common and cheap and lowering the size of transistors in the chip demands higher purity of the Silicon, so it makes more sense to me to just make the entire chip larger instead.

Edit: Great discussion going on here! It's all very interesting.
gpt
There are at least three good reasons.

The first is that smaller transistors require less electricity, as by being smaller, it just takes less energy to make them switch.  Owners frequently spend more on electricity to power a chip over its lifetime than they spent on buying the chip in the first place, especially if they're running it full time (like you might if you're a corporation or running a data center), so having smaller transistors is a competitive advantage.  You get to either provide more processing power in the same power envelope or the same processing power for less cost, either of which is good.

The second is mobile devices.  Power consumption is a huge deal there, so the first point is even more important than it is in larger devices, and in addition the physical size constraints are significant.  Every cubic millimeter dedicated to components is a cubic millimeter that's not being spent on battery capacity or making the device itself smaller, so smaller is better.

The third is that there's a limit on just how large a chip can be for a given clock speed, literally due to the speed of light.  Light can only travel about 30cm in a nanosecond, electrical pulses don't actually travel at the full speed of light, and current chips have clockspeeds in the 3GHz range, which means a clock tick is about 1/3 of a nanosecond.  Depending on how the chip is designed, you need to make sure that signals can travel some portion (possibly all the way) across the chip and then perhaps back again within a single clock cycle so that you can access all the cache and so forth, and it needs to do that with enough time that the transistors have time to reliably reach their new state if they flip.  If your chip is too large, that's just literally impossible, and you have to reduce the clock speed to make it work.