Since solder is such a poor conductor, why use it?

1)Consider the hundreds and in some cases possibly even thousands of solder joints within many electronic components. Why worry about a few more external ones?

2)In a properly soldered joint there will be extensive direct contact between the conductors being mated, so the resistance of the surrounding solder shouldn't matter.

3)The resistance of a properly soldered joint is likely to be negligible compared to the resistance of the wire being soldered, due to the great disparity in length.

4)In many applications, especially line-level analog interconnects, fraction of an ohm resistances will be totally unimportant anyway. Assuming, that is, that the line-level components being connected are not susceptible to ground loop issues as a result of poor design (in which case the resistance of the ground conductor might be of some significance).

Regards,
-- Al

09-25-15: Tbg
Timrhu, yes solder is awful now. It cracks.

I don't doubt your word if you have experienced that, but it needn't be so. Consider the hundreds of thousands and in many cases millions of solder joints in the avionics systems of military aircraft, which are accomplished mostly by automated soldering processes. Those seem to do ok, despite being exposed to extremes of vibration, temperature, and other environmental factors.

Regards,
-- Al

The link Larry provided is a good summary of wire wrap technology. With respect to its (non-)applicability to audio, though, in addition to the cost factor I would highlight the following paragraph:

Wire-wrap works well with digital circuits with few discrete components, but is less convenient for analog systems with many discrete resistors, capacitors or other components (such elements can be soldered to a header and plugged into a wire wrap socket).[2] The sockets are an additional cost compared to directly inserting integrated circuits into a printed circuit board, and add size and mass to a system. Multiple strands of wire may introduce cross-talk between circuits, of little consequence for digital circuits but a limitation for analog systems. The interconnected wires can radiate electromagnetic interference and have less predictable impedance than a printed circuit board. Wire-wrap construction cannot provide the ground planes and power distribution planes possible with multilayer printed circuit boards, increasing the possibility of noise.[3]

For those reasons it is pretty much inconceivable to me that something like a high resolution DAC, a high gain phono stage, or any number of other examples that could be cited, could be implemented successfully with wirewrap construction. And then there are the high power devices in power amplifiers, that require special mounting, heat-sinking, and heavy gauge connections ....

Also notable:

Surface-mount technology has made the technique much less useful than in previous decades.

Regards,
-- Al