Hello . For your question, I think that these people don't believe that there is end for everything. especially for the life.They shuold believe that the death is something real can come any time without feeling from us. That's why, they must think about it in order to improve their lives and do some good things to save them at the end of the world. However, that doesn't mean they must never think or have some fun time. In fact, they should enjoy their days one by one. Thank you. Good bye.