Life is just a raindrop in the ocean of eternity.
Without an afterlife, the length of life no matter the length, would be arbitrary.
Without purgatory no one could get into heaven since nothing unclean may come into His kingdom. Jesus didn't die for our sins so we could do whatever we want and simply be forgiven. What, then, would be the purpose in trying to be a "good person" aka a follower of Christ?
Todays life in some ways mock the life of our souls when we pass.
If we do something bad, such as steal, we get a small penalty...maybe get a fine or do some community service. If we do something, like murder, we get a larger penalty...maybe 20 years in prison.
Purgatory works the same way. We have to pay for our sins. Sins can be large or small and have consequences, receptively. We have to ready our souls for heaven just like we need to ready ourselves to go back into society after we commit a crime.
Simply put, sins are not all equal. If we murder two people, the penalty will be greater...perhaps life in prison. Purgatory, again, works the same way. Just because we have done one sin, doesn't mean it is okay to that sin again. They add up, just as crimes do.
If none of this is real and heaven and hell don't exist, what happens? Do we never see our loved ones again? My grandparents were married for 63 years. Do they never see each other. Is my grandmother or your grandmother just buried in the ground and that is it?
For those who believe, is God your King all of the time, honestly?
If we are honest with ourselves, which is difficult to do, He is only our King some of the time.
If God came down right in front of you and me TODAY and told us what we cannot do, would we be more serious about it? If he said don't use contraception, don't masturbate, don't have premarital sex, don't have oral or anal sex, don't have sex for simple pleasure, don't have sex with the same gender, would we listen?
These things are PROMOTED today as an okay thing to do. This is serious stuff.
If Jesus came to us TODAY how would we change our lives. He said not to do these things yet almost everyone continues to. If we are honest, we are followers of Christ SOMETIMES. We need to live our lives as if Jesus came and told us these things today in person if we wantt o be true followers of Him.