the cost of coating a part (that 99% of owners will never see) is millions of dollars.
Its a musclecar. Its meant to be cheap and fast. I can't even remember how many times I've looked under the car other than for work. How many friends of mine ever asked, "Hey can I look under the trunk??!"
Suck it up. Quit whining about some unimportant rust that does nothing from taking away from the driving experience.
Sit down, Shut up and Drive!