Are manufacturer AC cables good enough?

Why would a manufacturer ever sell their equipment with a poor power cable or a power cable that makes their product sound poor?
No kool aid here.

No doubt there are many of you who have decided that throwing money at a power cord is a necessity. I almost did the same...almost. I was later told (by someone in Binghamton) that McIntosh power cables are specifically designed/included with their gear and that there is no need for aftermarket. I was advised to use the money for more music or other components. I took the advice.No Kool Aid here.