Flexibilty - If I were to hard wire, then trying different power cables down the road becomes more of a chore. When I find a reasonable silver conductor I would like to try it with minimal fuss.
AND - a/b comparisons are much faster :-)
The xlr connectors I use for the 12v side are high quality gold on copper that perform extremely well. After all, If they are good enough for interconnects then they are good enough for power :-)
The IEC chassis mount socket is gold on copper, as are the connectors on 120v power cables.
Re: Kimber cable - the reason for using this is twofold - great quality copper and insulation and the braiding rejects ref interference.
I looked at a real heavy duty Furutech interconnect for the 12v side, but it would have cost a small fortune. The Kimber is great :-)