Holy Revelations and Death penalty

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Religions usually introduce very severe punishments for small crimes. Cutting off a hand for stealing and stoning to death for adultery are examples of the mind set shown by God's religions.

I always wondered about these. Why these cruel punishments? Why?
Religious people justify these acts by claiming that you cannot control crimes without severe punishments, to set an example for others… and this way the crime rate goes down.

I had doubts about this claim. The truth started to emerge when I began analyzing actual data. Factual conditions were opposed to this logic. I found that severe punishment does not affect the lowering of crime rates in any country. In fact it's the social, political and economical setup of the country which produces the crime rates.

At this writing many countries have passed laws regarding the death penalty:
94 countries abolished the death penalty for all offenses;
10 countries abolished the death penalty for all offenses (except under special circumstances);
35 retain the death penalty, but have not used it for at least 10 years;
58 retain the death penalty.

There are many countries which abolished death penalty in all crimes. Canada abolished death penalty for all offenses in 1975. In Canada, for example, the homicide rate per 100,000 population fell from a peak of 3.09 in 1975, the year before the abolition of the death penalty for murder, to 2.41 in 1980, and since then it has declined further. In 2005, 29 years after abolition, the homicide rate was 2.0 per 100,000 population, which is surely lower than when the death penalty was abolished. (amnesty Int.)

Why do religions emphasize the death penalty for many crimes? If reducing crime was the main objective for these punishments, then we already know it does not work. Rather, data now clearly shows that countries which have abolished the death penalty are showing a DECLINE in overall crime rates.

Under Islamic Law, murder is treated as a civil crime and is covered by the law of qisas (retaliation), whereby the relatives of the victim decide whether the offender is punished with death by the authorities or made to pay diyah (wergild) as compensation.
Very strangely, other crimes are considered to be more cruel than murder. Islam shows zero tolerance to these crimes and gives the most severe punishments to those offenders. Most of these crimes are sexual in nature. Why there is no diyah or wergild for these crimes? Are these crimes more severe than the killing of a person?
The following are crimes in which Islam shows no forgiveness of any kind, with death as a penalty:
"Treason, apostasy (renouncing one's religion), piracy (armed robbery), murder, terrorism, rape (including pedophilia), adultery and homosexual intercourse."

Now a very serious question arises ....

Is the God of this world so ignorant that he cannot figure out that human beings are not going to stop committing crimes when threatened with harsh punishment? Is he so primitive that he cannot understand all of the factors involved in different crimes?