It doesn’t act as a deterrent due to the crimes it’s used as a punishment for - no punishment stops a mentally Ill serial killer, someone in mindless rage acting on impulse, or someone who is certain they will never get caught. The studies all agree with that.
But if you would get sentences to life in prison or death from a parking violation or not paying your taxes, there would be zero people doing them as both are conscious actions, and definitely not worth the risk.
How does putting someone in jail or having them pay a fine to the government help “make the victims whole” any more than the death sentence would? If that was the point of the justice system, we would only have payments of wealth or services from criminals to victims and nothing else. In fact, I can think of quite a few crimes where the victims would love nothing more than the permission get to kill the criminal themselves in the most painful way possible.
The number one priority of a justice system is to prevent crimes from happening in the first place - a task it has to constantly balance with freedom and human rights as the ultimate solution is to get rid of all criminals - and the more it wants to prevent a certain type of crime, the harsher the punishment for it should be. But as I said, usually the death penalty is used for crimes done by people who aren’t thinking about the consequences.
If you use it as the threat for financial crime, soon you will have no more victims of financial crime, as the criminals are all either dead or too afraid to do it.
Should it be used, for that or in the first place, that’s a completely different argument all together.