The truth is that the more a cult is difficult the more appealing it becomes. It is in a human psyche that we appreciate something for which we strive harder and do not value things that we find easily or freely.  

See the other dangerous cults like the cult of Jim Jones or the cult of Shoko Asahar, the Mooni or the Heaven’s Gate. These were not easy cults at all. People handed all their belongings to their cult leaders and left their jobs to follow them. They lived very austere lives. Generally abstaining themselves from sex while the cult leader had full access to sex. In the case of David Koresh he told his followers women belong to God and since he was the messiah they belong to him. So he slept with the wives of his followers and with their teenager daughters. But he preached celibacy for men.  Shoko Asahara, Jim Jones and basically all of them punished severely those who disobeyed them and the followers thought the biggest punishment is excommunication. These cult leaders would ostracize those members who asked too many questions and these idiots sometimes committed suicide thinking God and his messiah are angry with them and hence life is not worth living anymore. Or perhaps they committed suicide to prove to their leaders that they are loyal and in this way seek forgiveness. Muhammad used this kind of punishment too. Ka’b the poet of Medina tells his own story of being punished by Muhammad with excommunication for 50 days during which time no one ever spoke to him and his wife left him.  

All the cults demand sacrifice from their followers. This is the way you can prove your faith and loyalty. You will gain the pleasure of "god" or the guru by sacrificing everything even your life. Cults praise hardship and disdain easy life.  

Scientologists know that too. They have different levels of courses. Level one will cost you about a dollar for every hour of course, as you advance you'll be asked to pay more. One man who paid $1,200 in advance for a 50 hour course completed it in 20 minutes, which meant he spent about $1 a second for auditing.  The rationale is that the more you pay for something the more you value it. "Nothing is expensive when your happiness is at stake." That is why all the cults are difficult to follow and they require sacrifices from their followers. To encourage his followers to sacrifice Muhammad said: 

" Not equal are those believers who sit (at home) and receive no hurt, and those who strive and fight in the cause of Allah with their goods and their persons. Allah hath granted a grade higher to those who strive and fight with their goods and persons than to those who sit (at home). Unto all (in Faith) Hath Allah promised good: But those who strive and fight Hath He distinguished above those who sit (at home) by a special reward,-(4:95)

The more dangerous a cult is the more difficult it becomes. In fact some cults won't accept you as a full member until you prove your loyalty by making huge sacrifices, which are considered as the test of your faith and devotion.  So the trick works. If it was easy no one would have taken it seriously.  

The cult leaders know this weakness in human psyche. They are psychopath narcissists. Control and domination comes natural to them. They love to be demanding, they love to see people do strenuous tasks for them so they feel the power and savor the sensation that they are in control of others people's lives. These fools will do anything their gurus tells them to do, including waging war for him, killing for him and sacrificing their lives. This feeds the narcissist's craving for power and control. It works like hand in glove. The cult leader enjoys the power and his benighted followers think because he is too demanding and harsh on them his cult must be true.

Why in the world the followers of the cults accept to be punished even physically when they can easily walk away and never come back? It is because the harsher a cult is and the more sacrifice it demands, the more believable it becomes. 

All cults have very rigorous rituals. The believers, become obsessed to follow these rituals to achieve salvation and are warned that if they fail in performing these rituals rightly they are committing major sin. They become slaves of mindless rituals that they perform, allegedly to please God or to be "enlightened". In this way the cult leader keeps them in his perpetual leash. 

Islam is one of the most demanding cults. Muslims are to wake up at early hours of the mornings to perform the ritual of fast and abstain from food and water for long hours. They are supposed to perform obligatory prayers five times per day. (Funny that in one hadith Muhammad claimed that Allah originally ordered 50 times prayers per day and he bargained with Allah to reduce it to 5 times only. In this way he wanted to make Muslims grateful to him for being kinder than Allah and trying to make life easier for them.) These prayers are constant brainwashing. You drill some jumbo mumbo and perform these automatic and moronic exercises and keep brainwashing yourself. 

Muslims are asked to abstain from certain foods, from listening to music and from socializing with the opposite sex. If they are women they must cover themselves in layers of veil in the scorching heat of the summer. They must cut their ties with their non-Muslim family and friends. These are all hardships and sacrifices that make a believer think he is gaining something precious in exchange. 

Instinctively we humans think "no pain no gain". Even our primitive ancestors used to give sacrifices including their children to appease their gods. 

Humans think the bigger is the pain the greater is the reward. These hardships in Islam, and in all cults, are in fact their main appeal. We humans think anything hard is better than anything easy. The harder a cult is, the truer it appears.