The big challenge
The big challenge for power cords are extreme current peaks. They are caused by the connected devices themselves through the conversion from AC to DC, since the capacitors of their power supplies can only be charged if the applied voltage is higher than that of the capacitors themselves - and that is only a brief moment in the voltage peak of the alternating mains voltage.
What remains are current spikes up to needle-shaped pulses with a multiple of the rated current of the devices. Because the capacitors discharge until the next peak, this process is repeated 100 times per second at 50 Hz or 120 times per second at 60 Hz mains frequency.
These extreme current peaks cause a whole series of unwanted effects. On the one hand, they cause substantial voltage and thus power losses in line and contact resistances. On the other hand, they cause strong magnetic fields which, due to their steeply rising edges, lead to significant skin effects even at the relatively low mains frequency. These reduce the effectively usable conductor cross-section. Furthermore, the magnetic field peaks disturb all other devices in their environment like small pinpricks. Particularly in demanding and dynamic passages in music, a great deal is demanded of the power supply and thus also of the mains cable.