There is no trophie but the Seasonal Events together with Online Multiplayer is what made the owners play it every week... so it's one of the biggest part of GT5 and the most popular too.
The Seasonal Event was created to make the Carrer replay infinite... there ware always a new and different Carrer event to play every week.
Forza 4 is easy... you can use any car below the limitation and win the race without see other car... you play alone because the AI is so dummy that make you feel like you are racing alone... if you start first you end first... no challenge.
Stop with the bs ethomaz, you just can't do that. Play Forza 4 before you judge the difficulty. Seriously, is that too much to ask for?
If you don't use a car right at the upper limit of the performance classification, with AI on Hard, in a proper race, you have absolutly no clance of winning. Playing later races in Forza 4 without a car at the top end of the performance index is like wining races in GT5 without a Corvette ZR1, but several times harder.
I can say this because I've nearly beaten both games, you can't because you only played Forza for an hour or so at a friends house.
P.S. If seasonal events were such a huge focus of GT5, why are there no trophies associated with it? Maybe to you it's a huge part of the game, but when I had a working PS3, I didn't even notice the mode, and I bet out of all the people I know who play GT5, you're the only one who noticed this mode.
Also p.p.s. Before you go on again and say Forza 4 is easy, play the game on anything but intro levels. TRY, JUST TRY, to come close to my Top Gear Track time. If you can't even come close to my time, you can't tell me what's hard/easy.