As a writer and reader I disagree with this. Perhaps if you are writing for a scientific journal or business report, long blocks of text can seem like you have a lot of info. Generally speaking, especially in fiction and non fiction i think unbroken pages of text will best case scenario bore a reader, worst case scenraio burden and overwhelm them with a lot of info so the feel daunted about continuing.
They tend to write about it because they have probably experienced it themselves or have felt the pain from others
I personally always include:
Why You want the job
Skill lists. You never want to be a one trick pony.
Bloat about your knowledge to the job to which you're applying.
Your educational accomplishments.
And include little about yourself,( not too much bcz, the employer really wont care. they just want someone ready to do the job.)