The question is not just the state of the victim, it is (mainly) the intent of the perpetrator and the means used. That's why you don't get the same sentence if you harm somebody by accident or if you meant to do it.
The sentiment that sentencing is justified by retribution is the number one reason why the US criminal justice system is messed up. The concept of right-and-wrong and mens rea are inextricably one.
Intent. Both fraud and theft require intent, rear ending a car can happen regardless of intent, and would be a much more severe charge if there was intent.
In both theft and fraud, the victim is deprived of of something. That’s why people consider them similar crimes.