Why do most religions teach that all "good" people go to heaven when they die?

Because they have been taught that they have an immortal soul that lives on after they die! Christendom’s Clergy uses this to control and rule over their congregations, give to the Church, confess your sins and attend church weekly and you are a good Christian, but is this what the Bible teaches, “no” it doesn’t but the uneducated person they like what they here (2 Timothy 4:3, 4) For there will be a period of time when they will not put up with the wholesome teaching, but according to their own desires, they will surround themselves with teachers to have their ears tickled. 4 They will turn away from listening to the truth and give attention to false stories.

Everyone likes to believe their loved one is in heaven when the Bible clearly states the opposite (Ecclesiastes 9:5, 6) For the living know that they will die, but the dead know nothing at all, nor do they have any more reward, because all memory of them is forgotten. 6 Also, their love and their hate and their jealousy have already perished, and they no longer have any share in what is done under the sun.

The Bible does give hope for those that have died (Romans 6:7) For the one who has died has been acquitted from his sin.

Because of this we see what happens to those that have died (Acts 24:15) And I have hope toward God, which hope these men also look forward to, that there is going to be a resurrection of both the righteous and the unrighteous.

Notice that both the good(righteous) and the bad(unrighteous) will be brought back in the resurrection of the last days! This is what all those that believed in Jesus believed, look at what Martha said about her brother and when she thought he would be resurrected (John 11:24) Martha said to him: “I know he will rise in the resurrection on the last day.”

Christendom’s clergy uses fear of a burning hell to get rich, just look at the Catholic religion, it’s believed to be the wealthiest religion, they didn’t earn their wealth by working it was all donated by some of the poorest people in the world! Plus the rich think the can buy their way into heaven!

(Ezekiel 18:4) Look! All the souls—to me they belong. As the soul of the father so also the soul of the son—to me they belong. The soul who sins is the one who will die.

What Does the Bible Really Teach? Is a free download at jw.org

After the death of Jesus’ apostles, by the beginning of the second century C.E., the early Church Fathers gained prominence. Describing their teachings, the New Catholic Encyclopedia (2003), Volume 6, page 687, says: “The general stream of teaching was that heavenly bliss is granted to the disembodied soul immediately after whatever necessary purification follows death.”