> Why couldn't we just label the resistor with silkscreen? We already decided labeling their drawer was better than labeling the resistor, so why not apply the same to the PCB? Easier to read silkscreen than color bands anyway, right?

Some resistors are labelled with silkscreen. Those resistors are expensive 1%, 0.1%, or 0.01%.

For run of the mill resistors it's cheaper to use colour coding. Also, when assembling a PCB it's good practice to keep the codes visible. That takes extra time for human operators. I don't know how machines do it for conventional components.

Labelling the PCB is important. There's a space marked R1, and a parts list telling us what R1 should be. There's a resistor in that space. How do we know what that resistor is? We read the color code, or the marking on the device.

There could have been a mistake at the resistor making factory, so we have a goods-in inspector who does some checking of the goods coming into the factory, and we buy from quality vendors and quality manufacturers. We hope the ISO 900x accreditation means something; we hope the certificates of conformity mean something.