In order for a proper fret level to take place, it requires the guitar to be assembled, strung up to pitch under tension, and acclamated. Then, your qualified skilled technician will go through a detailed evaluation process determining where his efforts need more attention and less attention elsewhere. Each neck is an individual piece of wood, and therefore reacts differently in sometimes subtle, and sometimes very obvious ways. Measurements are taken and recorded, and referenced while the leveling is done and it takes time to do right, and well. Then of course comes the crowning and polishing.
Warmoth is licenced to make "Parts", not guitars. Therefore, they perform no assembly as to not violate licensing agreements. Even if Warmoth performed this service, it would drive the price to the consumer up drastically due to the labor involved. Even then, an individual guitar setup is a very subjective concept, meanting that "you can't please everyone", and this is also very true in combining with manufacturing. Subjective concepts such as a guitar setup are best left to and individual's personal technician to allow for the owner to consult with, and inspect for quality assurance, the work being performed. If adjustments in setup are to be made, it is best to inspect and instruct in person than to be dealing with additional cost such as shipping, and then the customer service back and forth discussions over other details.
Warmoth makes the most precision detailed quality bodies and necks in the business, while remaining profitable, which is a rare thing in the manufacturing industry alone, not to mention the very narrow market of guitar components manufacturing.
I've seen 5K$ LP's at Guitarget that don't play nearly as well off the shelf as some of the Warmoths I've assembled personally, and others that co-workers and friends have done & I'll put my $$ on the Warmoth any day of the week.