Simple answer: 80% of the people in college have no business being in college. They don’t have the intellectual background, they don’t have the intellectual skills. They cannot read, write, or compute at college-entry level, nor have they any understanding of logic, ethics, literature, the classical arts, or the basics of chemistry or physics. And I say this as an online instructor who would be in the poorhouse if they all ever came to their senses and gave up trying to be college graduates.
That may be more or less true, but as a mediocre H.S. graduate myself, I believe they should be able to write sufficiently well regardless. And as another poster expressed, doing a lot of reading is key. Find out what the reading level is and you will likely see a correspondence.