Can't get free cars for all profiles!

Just purchased Forza 6 for Xbox one with the 10 year anniversary car pack. On my profile I get all of the cars. On my son’s profiles they have to buy the cars. You can’t purchase the pack again because it was already bought. Is there a fix for this problem. Why do they not get all of the cars?

This is normal for all FM6 DLC.

Only the actual account that buys the dlc will get the dlc free in game for the first purchase
All others will have access to the dlc if the console is set as that first accounts home console but will need to use in game credits to use them
VIP is different again and only applies to the account that buys it
If you really need to buy it again you can go xbox.com and log onto the account and buy it with real money again
Credits are that easy to earn in game so that would just be a waste of real money