Agree, but I also think its a sales pitch so the store makes more money. They know that newbies don't know jack about wattage and required size that would run their system smoothly. Adding huge wires does not do any justice as the amp is only going to drain the required current draw. Don't forget the distribution blocks, lugs, conduit cables to protect cables in engine bay all add up to the costs.
Back in the old days when car audio was young, most subwoofers had just plain speaker terminal inserts, An example is a Cerwin Vega XL-12, and not forgetting the iconic Cerwin Vega Stroker 12/15, all had spade terminals so you had to apply solder to connect speaker wired securely.
Most powerful subwoofers sold today, including some mid range priced ones have those five way binding posts with spring loading. The maximum size wires that could be fit in would be 8 gauge and that is sufficient for them as the subwoofers are tested before leaving the factory. Sometimes it seems everything is over-rated these days! :suave: