It’s marketing, imo. A 12 ga wire will work on any piece of gear. My 1200 Watt amplifier has a captive cord that looks to be a 14 ga wire. My saw pull 13 -15 amps and I ran it on a 12 ga wire. A 14 ga would work for short distance ie 30 ft. And I’m pretty sure a 14 ga would work on most gear except the highest power amps. But as I said earlier, my 1200.watt has a 14 ga.
So if a mfg has a 12 - 14 ga cable, it would be appropriate for all gear. However if a buyer believes that a 10 ga is necessary for their amp, they will pass by the 12 ga for the 8, 9, 10 ga of another mfg. Many times, marketing is determined by what will sell, not what is appropriate. So if the larger ga doesn't make for poorer sound then, it will sell better than the smaller but still appropriate cable.