Most people don't follow the messages sent before Islam, which also require self-discipline. Islam has the most difficult set of rules and most people don't have faith in anything, nor do they fear The Punishment enough to ever try to gain that faith. So the loss is their own.
I have to disagree still with Elijah Muhammad being a Prophet.
Prophet: A person who speaks for God, or by Divine Inspiration.
Again, when these men speak, their delivering a new message.
The message of Islam is 1400 years old. I'll say he was prophetic, but that's as far as I'll go. Muhammad (pbuh) was the seal of The Prophets. The later times (now) wouldn't want prophets or wise men. They'd want reformers and speakers. You can tell by how many so-called Christians make fun of Jesus (upon whom be peace) or at the very least, laugh when he's being made fun of. Clowing his lessons and quotes because ignorance is cool and wisdom just isn't.
If Jesus (upon whom be peace) were to come back today, very few people would believe he was more than some dude in a costume. Once his miracles were performed, they'd say it was magic or something stupid. The world doesn't want that kind of wisdom. You can tell just by how music is, that partying and other useless passtimes are more important to people than living by moral standards if not religious ones.
"Die before you die."-Prophet Muhammad (Pbuh)