You are being mislead. Vehicles no longer come fully factory undercoated and there's a good reason for it. Only about 15 States in the US actually use SALT on their roads in the winter. (Mainly Northeast & East Coast States). Once upon a time, EVERY vehicle from Factory was coated...and you paid for it to. It was listed right on the Monroney Sticker! Customers living in the other 35 States in the US were literally being FORCED to pay for something they did NOT need. After a lot of media attention and the involvement of the Government, Factories stopped applying this to ALL vehicles.
If you live in the following states:
Virginia
California
Iowa
Minnesota
West Virginia
Illinois
New Jersey
Maryland
Maine
Delaware
Indiana
Ohio
Wisconsin
Michigan
New Hampshire
New York
Vermont
Massachusetts

You SHOULD get undercoating. Most dealerships in these states offer it and it's not very expensive. (Couple hundred dollars). The only exception to this would be if you are purchasing a Mercedes Benz or a BMW because they still undercoat all of their vehicles.

By the way, I have been a toyota mechanic for 18 years and I can tell you that the Corrosion Perforation Warranty does not cover undercarriage corrosion. It only covers Side Panel Body Rust that is large enough to poke a pen through!

As far as paint protection, I think Toyota actually recommends this to customers. Mainly because the Consumer Product Safety Commission banned Lead-based Paint from being used on Automobiles in the US meaning you car is now more likely to get permanent damage from UV Rays, or even something as simple a bird crap! NASCAR even puts a protective film on their race cars!!!

I hope this helps!!!!