Why do automotive wiring diagrams use earth ground symbols?

I have noticed that a lot of wiring diagrams for vehicles often use an earth ground symbol instead of a chassis ground symbol. Is there a reason behind that?|||I think it came from many years of confusion in Electrical. Does the Proton flow to the neutron or does the neutron flow to the Proton. I am not sure of your age, but in years past cars could have either a positive ground or a negative ground in the automotive electrical. Those were pretty much in the Generator days before alternators became the industry standard. I would say as a standard...in electrical schematics...Ground is Ground. Meaning with out it..you will not have continuity in the completion of a circuit. Good Luck! Which came first the chicken or the egg?|||Why care? Ground is relative to all potentials in the circuit.