Are manufacturer AC cables good enough?

Do you people ever have time to listen to music?...I mean, with all this time spent on here posting and talking about "flat earth", arguing whether "water is wet or just moist?" etc etc...

I make my own from old-fashion style 12/3 round woven fabric cable, hospital grade plugs and lock-in IEC connectors 

kozka,
About 6 hours a day on average (more recently). Also, the earth isn't flat. 

How about Auto manufacturers? I’ve seen some pretty mediocre tires come stock, and on higher end cars better rubber. FWIW, Naim who are fairly conservative. Offer their own upgraded power cables and interconnects, their engineers can hear the difference, so do PS Audio, and I’m sure a few others. Power cords that come with equipment are adequate, and if one thinks that’s all that’s needed then fine be happy, but  don’t Be a Cable Cop !