Newchevyman

So i just purchased a brand new 2017 silverado wt model. When i purchased it they didn't have the second key so they had to mail it to me. I didn't really think about it that day but my truck did not include key fobs to unlock the doors. I was introduced to the mychevyapp which can unlock my doors and some other neat stuff. I called the dealer and they said i had the hardware but not the software so to program everything and get a key fob it would be $450.

so my question is if the app can unlock my doors why cant i just buy a fob and program it? Wouldn't it seem that the software is there?