The מסילת ישרים says that one of the ways to convince someone that it’s worthwhile to observe the Torah, is the concept of reward and punishment. We ask what the other person would do if the Torah’s punishments are accurate.
Is it worth taking a chance and violate Mitzvot, when the Torah is very strict in enforcing its observance.
The Talmud in סנהדרין says the following regarding how punishments are enforced even nowadays. One who did a transgression where he would be חייב סקילה, stoning, will either fall off of a roof, or will be killed by a wild animal. If one is חייב שריפה, death by fire, he will meet his demise in a fire, or will be bitten by a snake. If one is guilty of הרג, death by the sword, is executed by the government, or he is attacked by robbers. And if he is guilty of חנק, he dies by way of drowning in a river or choking or suffocation.
From all of this, it looks like a good idea to take the Torah’s punishments seriously.