Some people reject the Christian faith without ever giving it a proper hearing. The distractions of the world keep them from ever getting around to it. Some reject the faith because the way it is presented to them makes it unappealing. Others understand what they are hearing, and even see the appeal, but refuse to give up a besetting sin to which they are in thrall and so come to Christ.
These are reasons I understand, though I don’t agree with them.