It is definitely a throwback coverage to when many people did not have health insurance. It was also pushed on many states as mandatory so that hospitals/ ambulances could get paid for responding to an auto accident, even if the people were otherwise unable to pay. It is further supported politically by chiropractors and other providers who offer "free" care up front to those injured in an auto accident. It is also a half-measure toward "no-fault" auto insurance.
If you can decline it, AND you have good insurance, I think it's a good to decline. However, if you have a high deductible plan or a HSA, it might be worth it to keep. An auto accident is one of the most likely "unplanned" no warning financial hardships. It only takes a second for you to have no car, no transportation, and an injury. It can take weeks-months- over a year, to get compensated from the at fault driver. AND, if the other driver flees or has no insurance, you may bare all of your own costs.
So, if you have a $5,000 deductible health plan, do you have enough in savings that you could pay that deductible AND replace your car AND deal with 1-2 months out of work before being reimbursed? If not, that $70 might be worth paying until you do have that kind of savings.