Well, for at least a couple reasons. For one, RCAs have generally been overused in consumer electronics. They’ve been used for both audio and video connections, as well as digital signal feeds, and yes even for speaker connections, as Seth mentioned. Some of these applications require a different cable type. For instance, video and digital signals are best delivered with a 75-ohm shielded coaxial cable. Basic analog audio doesn’t necessarily require 75-ohm cable, but it does required shielded cable. Speaker wire, on the other hand, does not require shielded cable, which is why something like standard zip cord is adequate and indeed typically used.
IMO there should be a different connector type for each application. This is because confused people often get the wrong cable type for their application, thinking “it’s got RCA connectors, so we’re good.” If speaker wire (i.e. unshielded zip cord) with RCAs was commonplace, I assure you that forums like this would be inundated with people asking questions like “why do I have a hum in my system?” or “why does my picture have lines in it?” when they tried to use RCA speaker cable for their analog audio or video connections between components.
Second, it’s commonly acknowledged that good speaker wire should 14 or 12-guage wire. So, tell ya what: Get a piece of 14-guage speaker and wire a loose RCA plug from Radio Shack (or the vendor of your choice). Then see if you can figure out how to get the RCA’s barrel over that thick wire, much less solder it up without melting the vinyl the RCA’s center pin is sitting in.
When you think about it, once you attach your speaker cables to the banana plugs at both ends, you then have a “plug and play” cable. Just remember to go back and re-tighten all the screws in a year or so.
Regards,
Wayne A. Pflughaupt
