Again, we don't know what "PD are picking", we only know what the end result of their choices, the brands' choices, the negotiations over licensing, the contracts, the access to model, and the modelling is.
If a brand won't let PD use a car, or PD can't arrange access to model it, it doesn't appear in the game. There's also a case, particularly with race cars, where a brand that appears on the car may not want to allow PD to licence its logo. We've seen that worked round with the DBR9 but the amount of derision that attracted at the time may have put them off that approach; T10 is currently dealing with the same response to some recently added Porsche models.
It really isn't as simple as "I want car [x]* and PD hasn't added it so PD bad".
*Usually "[x] instead of [y]", which is nonsensical.