I don't think there is any such guide. At least if there is one, it will be limited to a few basic uses of the device.
The difference is that if you are using, e.g., a programming library, all you really need to understand is the API. The library is designed to do a few well-constrained things.
Now, a component like a transistor is also designed to do a single thing: a bipolar transistor controls the output (Collector) current by varying the base current. However, that single "feature" has huge amounts of leverage and hides a lot of complexity.
The same transistor can act like a switch: give it plenty of base current and it will saturate and conduct a lot of current.
It's a proportional valve: give it varying, small amounts of base current, and you will get a varying, larger amount of current conducted at collector-emitter.
It's a temperature sensor: give it a small, fixed amount of base current and the voltage from base-emitter will vary depending on the temperature. As a result, the current at the collector-emitter junction will also vary according to temperature.
My point is that the only useful "user guide" to a transistor requires knowing its fundamental properties. You may not need to remember the complete Ebers-Moll model, but you do need to understand the fundamental properties if you're going to use the device to its fullest.
Failing that, if you have a specific question, just ask. Lots of smart people here: someone will be able to help you.
Main (and probably only) reason: copper is expensive. I've commented before that cost can outweigh other factors in design and production, and that goes also for components. Every milli-cent counts. The alloy used (no, I don't know what it is) may have a higher resistance than copper, but over the whole the difference will be negligible. I guess that for very low value resistors (< 0.01\$\Omega\$) copper may be used. Copper is also used for certain power devices because it conducts heat better. These 500\$\mu \Omega\$ examples from Isabellenhütte illustrate both:
Best Answer
Because wires and traces are not perfect. They all contain some inductance which impede high frequency currents trying to flow through them.
Needless to say: Radio frequency = really high frequency.
The bad effects are increased noise, voltage spikes when the chip's current demand decreases and voltage dips when the chip's current demand increases.
So what do you do if are trying to move lots of water and all you have are tiny pipes? You use a bunch of tiny pipes in parallel. Parallel inductances results in an overall lower inductance.
Also, because IC packaging is standardized and if you don't need all those pins, you might as well connect them to ground because it reduces noise due to the aformentioned high frequency currents trying to flow through trace inductance.