How so? They're actually an improvement over past GTs. Soft tires in GT4, for instance, would only last less than one lap of the Nurburgring before they were toast. And I like the fact that tire temperature is now accurately displayed. When a tire is rolling straight, it's going to be cooler than it is when it's cornering hard. Track temperature is not simulated in GT, which is why they stay cool when they're rolling straight, but otherwise I'd say PD is in the right direction.
The only area they need work is with hardness/softness ratings. Hard tires should last longer than softs, for instance, assuming both are given near-equal amounts of punishment. The way it is now, there is not any reason to use hard tires during an endurance anymore, because softs seem to last just as long.
This could easily turn into a GT versus Forza discussion ha ha. I'm in the habit of thinking PD's terms "Comfort Hard" or "Sports Soft" are just like tire brands...albeit a bit on the generic side. It's like all the cars in the entire game are rolling on just one brand if tire.
Think of it like this: in America's Grand Am there's the Continental Tire Challenge. All the cars are running on (guess) Continentals, no matter which make or manufacturer. PD is sort of doing the same thing. There's a tire for the Veyron in PD, for instance, which has certain grip, temperature, and treadwear ratings, and the exact same ratings can be found on a similar tire for a Subaru 360. Only difference obviously is size. The 360 is going to have much smaller tires than the Veyron.
My experience with Forza is limited. I know they've managed to put real-life tire brands in the game, but opinions vary wildly as to how accurate of a job Forza did.
I think PD just doesn't want to deal with naysayers going: "well, that's not how a Michelin Pilot would react", so they just implment their own brand of tire, with three distinct classes (Comfort, Sports, Racing).