I'm not quite on board with the assumption that less cars equals better / more features. A 3D artist who's currently tasked with modelling non-Gr.3 cars would not typically start working on features like dynamic weather and time of day just because he ran out of cars to model.
In other words, I don't understand why the inclusion of other classes precludes PD from adding a specific feature.
Many people assume PD already have too much to deal with and should concentrate on tracks or weather or blue flames or clutches or penalties.
I mentioned before, putting how you feel about Gran turismo and want people want, would GT Sport be better as focused on one discipline?
Maybe that does allow for concentration on other factors.
What's the difference in PD deleting all other groups? In Campaign mode, does replacing Gr. 1 Endurance races with Gr. 3 cars, allow another part of the team to come up with more races?
Does having only Gr. 3 change the scope of major events like the Toyota sponsored event or the Asia/Oceania events?
What I'm getting at, are people's instinct to say, "because I want". I didn't initially buy GTS because it was online focused. Waited til March to buy it. Happy I did.
Same could be, if it were Gr3 only. Sure, we'll never know, because it is what it is now. However, if the game launched with Gr. 3 only, Campaign Mode, Arcade Mode. Maybe it'd be received better than at debut.