Why do NPN/PNP transistors need to use doped semiconductors for the 'N' region?

Question

By my understanding, as long as the P layers are properly doped (to have fewer free electrons), the electrons could not flow between collector and emitter until the P is given a satisfactory level of charge, as otherwise the base layer could not pull electrons from the poles. In this case, why can't the N layers be just made of simple conductors, like copper? What is special about the negative doping process that makes it different to just a conductor? Is it to do with polarising the flow of electricity?

E.g. on this diagram, why couldn't we just replace the red bits with copper, provided we keep the blue bit positively doped? More specifically, what is the difference between these regions and your standard conductors?

For reference, I really don't know a lot about this area: all of my knowledge comes from reading (this article)[https://www.explainthatstuff.com/howtransistorswork.html] followed by a skim though the (Wikipedia)[https://en.m.wikipedia.org/wiki/Transistor?wprov=sfla1]

Answer 1

going out on a limb here --- if the base region is a "sea of charges" then the injected charges will have approximately Zero Lifetime, because of near-instant hole-electron charge cancellation, and the Beta will be near zero.

Answer 2

From what I read it seems to me you're beginning reading up on transistors, and that perhaps you've missed an important point which admittedly many authors skip on - what is a transistor?
Because it is very important to point out where we want to go; what we want to achieve in the first place. You can get in as many complications as you want later on but where we started has got to be clear.

In very simple terms, a transistor is a device with at least 3 terminals: between two of these there's a flow of power; the other one of them controls such flow. Notice that the word 'control' also implies a predictable flow i.e. it can't be arbitrary. That's why e.g. a thyristor is not a transistor. A common analogy for the transistor is a water valve: the more you open it, the more water flow; and you don't get full flow if you, say, turn it just slightly.

I'm saying all this because what you "propose" entirely lacks the transistor effect - it's more like a resistor after all, actually a very expensive one. You don't just stick a doped semiconductor with three terminals and get a transistor - it's a lot more complicated than that and there's a lot of physics (pretty modern as well) involved.