They do have deposits for USD too. And I like this feature. I have a small deposit with namecheap (around $100) and it's good if I want to register my next domain instead of going through the CC transaction thing.
Deposits for USD are fine. If that gets stolen then their insurers and their bank's insurers will rectify the situation. Perhaps namecheap are offering the same protections for bitcoin deposits, I haven't looked at their TOS.