I tried looking at the documentation for Trac's (0.12) customizable ticket workflow.
The authors claim that it is completely customizable, but there is something I don't get then. There must be an "initial state" at which tickets start, I guess. Is this hardcoded as "new"?
Not only "new", "closed" is the other hard-coded Trac ticket status.
This was and is so for different reasons, among others these labels are used to do conditional formatting with fixed-name CSS classes, default reports use "not closed" as synonym for open tickets, etc.
As a related note, there is some work on the way to possibly lift this limitation in later versions (Trac 1.2 and beyond). Until then its really better to "work with it rather than against it", as JosefAssad said.