Because it's absurd to think a 1.5 second car advantage comes from tyre pressures. It's laughable.
Anyone can enjoy an advantage over the field if they have a superior engine and chassis. There is no evidence to suggest Ferrari have suddenly obtained this between one race weekend.
Once I was playing F1 on PS3 and after a few minutes tweeking my setup without any significative results, I've raised my tire pressures by about 1 PSI. Suddenly I was almost 2 seconds faster.
I'm just saying, if Codemasters implemented this in the game it might be possible.
Afterall you used this reasoning to explain why Vettel's tire exploded.