Miss Snark, you have to understand that people have read that scary Noah Lukeman book, The First Five Pages, and it says stuff like if there is even an itsy-bitsy-teeny-weeny yellow polka-dot indentation on the edge of a single page, then the agent will instantly toss the entire package, because obviously the fool supplicant is sending previously-viewed paper.
Yes I've tossed stuff that was hard to read without more than a cursory glance. I get tired and cranky and impatient with people who send me work that looks like they don't give a damn. Mostly though I try to at least recognize effort and remember sometimes writers just don't know what industry standards are.
If you write well enough, I'll let you send me stuff with coffee stains.
But the cold hard truth is that 99.9% of y'all are NOT going to write well enough AT THIS STAGE OF YOUR CAREER to get away with that.
Right now, you need to err on the side of correctness. Which means following the guidelines right down to "no typos" and "no coffee stains" and no "teeny weenie polka dot bikini indentations" either.
This is like the haircut before the job interview; it demonstrates you wish to be taken seriously.
Agents are looking for good writing. It's a whole lot easier to focus on the writing when the words are spelled right, the font is easy to read and the page doesn't resemble Jackson Pollock.