They serve the imagined "next life", not their current actual lives. They restrict their own and that of others, freedom, happiness, joy, fullfilment and potential for transcendance through creativity in art, for the promise of entrance into heaven. Thus the world loses value to the point of being completely insignificant compared to the afterlife. The afterlife is obviously here seen as nonexistent and an empty promise made by humans who subscribe to some fantasy world. By not striving for the purpose and possibilities for or in this life, they deny themselves the ability to live life to its fullest. Since this life is the only life, and the only chance you get to experience it is right now, however, they deny themselves this in exchange for nothing, meaning they are actually commiting to a nihlistic way of life, even if unknowingly.

Another way of putting it could be to say, they are making death (end of existence) more sacred, than life (existence).

This all requires you to acknowledge the nihilistic nature of the universe. That there are no Gods and there may not be any intristic objective meaning to reality, yet (and because of this), what we have now, is all we have, empty of true meaning or purpose as it may be, when the alternative is non existence, the only time you can make a choice regarding to live or not, is when we are living.

A metaphor could to a degree be used for celebrity obsession. In this case, you spend your energy on some human, who have most likely, barely any real significance in YOUR life. Thus in effect, you are quenching your own existence and its meaning or purpose, in service of some seperate entity, largely not real due to the fabricated view most people have of a celebrity. This fabrication stems from the fact that its doubtful that the "image" of the celebrity in any way truly corresponds to the actual person.