There's a huge drop off in affiliate revenue from GoDaddy to the next most popular registrar. Making Namecheap default would inconvenience most the users and cause a substantial drop in my revenue.
I appreciate where you're coming from, but I'm not sure the pros of switching outweigh the cons.
He's arguing practicality over principals. Suppose he switched to Namecheap and makes a third of his current revenue. Because of this change, the site operates at a loss and he is eventually forced to shutdown the service.
Which would you prefer? His site no longer being around, or be slightly inconvenienced by changing the default provider via a dropdown box?
I appreciate where you're coming from, but I'm not sure the pros of switching outweigh the cons.