Different branded aftermarket parts mean different performance variables for your car, not to mention endless upgrade possibilities, particularly varying exhaust and turbo/charger sounds.
Wow I guess some people have been living under a rock? Forza 5 has branded wheels and aero parts. It makes sense for those items because they LOOK different.
Branded parts for turbos, intercoolers, shocks etc are STUPID and a WASTE of licensing fees. Those parts all look the same and they are internal too so you can’t even see them during replays or driving.
You might be able to get free licensing if you show their name prominently enough. A game where most upgrades are yours and that is played by (a guess) three million people is brilliant for exposure… plus its optional, its a lot easier for T10 to walk away from a tuner (hence they have more bargaining power) when they can stick their name on all the tuning parts themselves if they have to, than say the M4 (you can’t just stick a Forza logo on instead of a BMW one).