I own a Model X and like ALL Model Xs it has hydraulic adaptive suspension, unlike our Model 3. Again, Tesla's places a focus on reducing variants. There used to be 7 colors for S and X. Now we are down to 5, and one of those, White Metallic, used to be an option and is the standard. It is cheaper for Tesla to use more expensive paint over and over then put it on only when someone pays extra.
This is something Honda brought to the market with the 1st Accords. They threw all sorts of things like A/C, power windows, etc in as standard, because it is cheaper to build them in that build some cars without and some without. Until then you might have 5-6 pages of options you could mix and match on a Detriot-built car.
As far as making adaptive suspension standard, my guess is if it gets cheap enough to do that they will. Unless they view Adaptive suspension as something that differentiates the X and S from the 3 and Y.