you guys should not forget that even a "simulation" is still just a game i think some real values are not really needed in a game... a physic should be close to real for sure but things like different engine power because of different track height or air temperature are a bit too off...
I agree with you that to add these things to our sims today would be a bit pointless when big features like dynamic weather and day/night transitions are still missing from some sims. Having said that though track elevation and air density would (I think) be fairly static values apart from maybe for very long circuits so I guess would be easier to include than track surface evolution which is already being done. It would be nice to have the choice though.
Maybe all those roads cars in AC would be a lot less fun to drive if they modelled the brakes properly and they all had terrible brake fade after 2 laps. Maybe that is the real reason they don't include it