Because they are absolutely scathing. Take Ezekiel 33:30-33
“As for you, son of man, your people who talk together about you by the walls and at the doors of the houses, say to one another, each to his brother, `Come, and hear what the word is that comes forth from the LORD.’ 31 And they come to you as people come, and they sit before you as my people, and they hear what you say but they will not do it; for with their lips they show much love, but their heart is set on their gain. 32 And, lo, you are to them like one who sings love songs with a beautiful voice and plays well on an instrument, for they hear what you say, but they will not do it. 33 When this [judgment] comes — and come it will! — then they will know that a prophet has been among them.”
In sum, you love to hear a good sermon, but you never pay attention to it.
I’m pretty sure very few Christians have ever heard a sermon on this passage.
Stay tuned. There are more such passages to come.