Because moral integrity is well-masked hypocrisy. There’s not a single moral philosophy system which is complete, meaning it’s not self-contradictory or doesn’t give rise to moral dilemmas and paradoxes upon close examination. Take a look some moral philosophy courses and you will find out that morality is unresolved. Every approach has flaws. Every system fails dramatically in certain situations.

It’s unresolved because it’s unresolvable - morality is a fundamentally flawed attempt to come up with a logical explanation for our emotions. To maximize the good feelings and minimize the bad. But these feelings themselves are, strictly speaking, irrational, and you can’t come up with a rational system to govern irrational things. What seems “fair” to one person doesn’t seem like it to another. What is suffering to one person is a minor inconvenience to another etc.

The only objective reality is that of your body. You will experience hunger, thirst, cold and physical pain regardless of your moral system. So the only objective morality is “do whatever you want to keep yourself fed and warm”. Everything else on top of that is a pretense. Note that this is also how animals live, and it wouldn’t occur to most people to call them immoral. And they don’t engage in insane projections into the future obsessing over maximizing their wealth or lifespan. Or gaining as much power as possible due to paranoid fear of hunger in the future. If they’re fed and warm right now, at this very moment, they are happy and harmless. It’s just nature.

For most people adopting such morality is a very hard and emotional process of stripping themselves of all the illusions of life, and in the end it means not having to do pretty much anything, because basic food and shelter is quite easy in most parts of the world. Everything else just becomes a play, an entertainment, a creative pursuit on top of an absolutely happy life, and it’s entitely optional. Such a person has no need to harm anybody, because there’s literally nothing to harm for. That’s pretty much what they call “spiritual enlightenment”, and it’s based on being honest about what’s real and what exists purely in your imagination.