What's the point of earning XP?
2 Answers
The point of earning XP in Forza Horizon 2 would be to advance up levels and wristbands. It's not a really important thing in the game but it compares you to other drivers. For example: If someone has level 999 and the highest color wristband it means that they are an extremely good driver.
The other use of leveling up in Forza Horizon 2 is to earn Wheelspins. These wheelspins can either reward you with Credits or Cars.
Note however that this only occurs on the Xbox One version of the game. The 360 version does not have Wheelspins.