What else do I need to grind for? I have an FGT and Only have endurance races left to do?
An example would be this, you need roughly (I'm
guessing) 2,500,000 (or more) experience points to get from level 34 to level 35.
Each endurance race you do does not give enough points for you to automatically progress to the next level .
The seasonal events do not give you this amount of points in one 'hit' i.e. if you did one set of seasonol events in one go either. Even if you combine both of these together, for some levels it would still not be enough to move up.
However, if you took your time and waited for each new set of seasonal events to come out, then yes,
you would be correct, eventually you would progress to the next level - wthout any grinding.
I had already reached level 30 before update 1.05, so I didn't have the benefit of the seasonal events, I had to grind to move up. You have only just reached level 25, so now you have the benefit of these races.
Also, it's not just about experience points, some people grind for money so they can buy the cars they either want to collect or drive. There's different reasons for grinding and people play this game in different ways because they want different things from the game.
Add to this the difference in time people have to actually spend playing the game and the different skill levels of people who play this and there's alot of diffferent variables as to whether people grind or not, and if they do how much of it they do and what they are doing it for.