When I was growing up, I had a large number of friends that had different Christian beliefs. Some of them were Catholic, and some held to protestant views. Many of them agreed that the general plan for humanity after life was over involved a judgement before God and an eternal life in either heaven or hell. Though we never had long discussions about these subjects... there was a general consensus that going to heaven meant living with God in peace and happiness, and going to hell meant perpetual torture at the hands of the devil.
As a latter day saint, my instruction in the plan of salvation was a bit more complicated than the view that humans were created here on earth, and that based on our faith or behavior (or a combination of faith and behaviors) we would be assigned our eternal destination of eternal peace or eternal pain.
The Mormon view of the plan of salvation involves life beginning before mortality... such that being called children of God was not some figurative statement representing divine affection for humanity. Similar to other views, it included mortality, and at death, some form of judgement where people would be assigned a destination of peace and rest or pain and confinement... but that these places would only be temporary. After the end of the earth, there will be another judgement wherein people will be assigned permanent destinations in one of three kingdoms of differing glories.
Some people found this interpretation confusing, and inconsistent with scripture. Of course, few of them were aware of the passage in 1 Corinthians 15:40-42:
"There are also celestial bodies, and bodies terrestrial: but the glory of the celestial is one, and the glory of the terrestrial is another. There is one glory of the sun, and another glory of the moon, and another glory of the stars: for one star differeth from another star in glory. So also is the resurrection of the dead. It is sown in corruption; it is raised in incorruption..."
In my young mind, I believed this settled the question, but as I grew older, and read from the scriptures more on my own, I became confused as to why so many prophets and scripture passages used the heaven and hell model if it was incomplete.
Consider in the Book of Mormon, 2 Nephi 9:34 - "Wo unto the liar, for he shall be thrust down to hell." What does that even mean? A person who lies (and presumably does not repent of this sin) will be sent to a lake of fire for perpetual torture? Or a person will be uncomfortable for a temporary amount of time until final judgement where they will inherit a lesser kingdom? Why say "hell" if it is so ambiguous?
Consider also the imagery in 2 Nephi 9:15-16 - "And it shall come to pass that when all men shall have passed from this first death unto life, insomuch as they have become immortal, they must appear before the judgment-seat of the Holy One of Israel; and then cometh the judgment, and then must they be judged according to the holy judgment of God. And assuredly, as the Lord liveth, for the Lord God hath spoken it, and it is his eternal word, which cannot pass away, that they who are righteous shall be righteous still, and they who are filthy shall be filthy still; wherefore, they who are filthy are the devil and his angels; and they shall go away into everlasting fire, prepared for them; and their torment is as a lake of fire and brimstone, whose flame ascendeth up forever and ever and has no end."
Why describe everlasting fire, and torment as a lake of fire and brimstone with unquenchable flames if these things do not exist?
Even Jesus himself said "...but whosoever shall say, Thou fool, shall be in danger of hell fire." (Matthew 5:22)
Ultimately, the idea is that sin is bad. This is particularly important when discussing sinful behavior that does not seem to produce harmful consequences. If two adults consent to extramarital intimacy, who is getting harmed? If a person decides to indulge in some substance abuse in the privacy of their own home, who is getting harmed? If a person decides to steal from someone who has an abundance of wealth and insurance to cover their losses, who is getting harmed? If a person takes credit for things they did not do, what does it really hurt if they gain a small advantage?
It is a constant need for religion to convey the seriousness of actions that do not seem immediately harmful. Unfortunately, the difficulty in doing so increases when faiths get into petty arguments regarding minutia and ignore elements that can truly erode the moral strength of society. As time has passed, it has become increasingly popular for those who seek to establish secularism to mock those who try to maintain protections for time-honored social values. Some of this mockery is even understandable as there have been some who have used religious and other persuasion to benefit themselves rather than their congregations or society in general. Requesting evidence and clarity can help reduce the influence of falsehoods that inflate themselves with religious imagery such as ascending flames, lakes of fire, and perpetual damnation.
That having been said, the idea of hellfire and damnation is still important where the deeds of individuals cause unseen harm. Whether the actions involve drinking contaminated water, avoiding potentially life-saving vaccinations, or transgressing the commandments of God... these deeds can result in actual harm. Though the victims of bad water or a lack of vaccines can be observed to have been harmed in a relatively short period of time... the victims of some sinful behavior may not be revealed in a single lifetime, but that does not mean the crimes are imaginary. The real victim of transgression actually experienced the torturous consequences of this behavior... and it is his prophets and apostles who through the ages have described the effects as being like unending flames, perpetual torment, and lakes of fire and brimstone. In any sin, Jesus Christ is a victim. The thoughtless idle words and deeds of men literally caused a person to endure such crippling pain that blood oozed out of his skin. (Luke 22:44)
These actual consequences of sin fall upon those that commit them unless they agree to accept the saving power of Jesus Christ... which literally saves men from having to endure these horrendous ordeals. Understanding not only that God has tremendous rewards for those that heed his words, but that he literally seeks to prevent tremendous harm from coming upon us, should motivate us to better keep his laws. No doubt, there are many reasons to choose the right... and even if avoiding hellfire and damnation are among them, then humanity is better off than it otherwise would be.