If NCL were to homeport in Norfolk I'd guess they would put an older, smaller ship there, not one of their large fancy new builds.
NCL has huge homeport operations in NY and FL where there's always a market demand for bright, shiny new toys and competition amongst the cruise lines as to who has the newest and most tricked out ship.
A secondary homeport like Norfolk is where you're going to find passengers who will cruise for the convenience of not having to travel to NY or Florida and where you won't be competing with other cruise lines' newest hardware.