Stephen Schwartz points to a number of reasons, such as the threat of being expelled from their mosques.
One of the things that has always polluted religion is the tendency of clerics to resort to strongarm tactices to enforce their views of doctrine. That's why the Catholic Church became a worldly power and kept its people ignorant and its scriptures in Latin. It's why the Rabbis dominate Judaism after the Temple in Jerusalem was destroyed and the priests who had officiated there no longer had anything to do for a living. Rabbis are what the New Testament calls "scribes" and "lawyers." They have no real authority from God as the Levites and the Sons of Aaron had. They saw a vacuum and moved into it. The same thing happened in the Christian churches when the Apostles, who were the source of revelation and guidance from God, disappeared. The remaining bishops, who were all local authorities with equal powers argued and wrangled over doctrine for many years accusing each other of heresy until the strong won, and the weak were burned at the stake. Is that how God operates?
Islam's prophet, Mohammed, may or may not have been a true prophet, but either way, we have his revelation through a long period of oral transmission and editing by scholars who themselves had no authority. Such people invest everything in their own interpretations and fear authentic revelation. They use the worldly powers of censorship, money, personal attacks and even violence to hold on to their influence. It is no surprise then that when the Saudis became fabulously wealthy, their Wahhabism began to spread throughout the world's Muslim communities, through training Wahhabi imams and building Mosques and furnishing literature to be read by young Muslims.
Islam teaches that there is nothing especially sacred or holy about a mosque. It does not have the concept of a priesthood or any true central authorities as the Jews once did or as the Catholics do today. By what authority then do Wahhabist imams threaten people and exclude them from mosques? The only authorities in Islam turn out to be their version of Rabbis and Bishops, people who obtained educations and were able to cite philosophy and learning to support their positions.
Mohammed taught that all Muslims are equal, but it hasn't turned out that way. When there is a vacuum of power, it will be filled by those who desire power.
The Muslims, Jews and Christians need to turn to God personally, pray to him from their hearts and ask what they should do, not in prayers written by others, but speaking their own words to him and listening to their feelings. God communicates through the spirit which is decribed as a still, small voice, dreams and visions, but those revelations only come when one is persistant is being humble, penitent and virtuous. There are some easy ways to recognize truth, however. It doesn't come through people who exclude others from their churches or assert that without learning people are less worthy of esteem. Anybody who calls upon his followers to kill people as infidels or to deprive others of their freedom to choose what to believe or how to worship is not from God.
For this eternal truth is given,
That God will force no man to heaven.I believe that if Muslims could read the Book of Mormon without being intimidated, they would find that revelation has not ceased. Prophecy has not ceased. God's love and involvement with mankind has not ceased. False prophets abound, but he will show those who approach him sincerely and humbly where to find his truth.