(Thanks to circumstances beyond my control, I'm not editing today.)

I've noticed a tendency among writers who haven't worked in publishing to be kind of dismissive of stuff like grammar and spelling. This is in strong contrast with those who have worked in publishing: That's a field where the term "functionally illiterate" (say it with contempt!) is applied to those who make these types of errors, no matter how many PhDs or billions of dollars they may have. It is also a field where cover letters containing errors are marked up with red pencil and hung on the wall in the break room for the amusement of staff.

Outside that world of hedgehogs, less-experienced writers sometimes regard grammar and spelling as mere details (because when it comes to writing, details don't matter). I have even heard proofreading disparaged as "technical editing," with the implication that grammar and spelling are mere technicalities that a true artist can dispose of. You know, the way Michelangelo disposed with learning how to paint. (In addition to being bad in concept, that is also a misuse of the term: Technical writing and editing is what you do when you produce technical documents--user's manuals and the like.)

The fact of the matter is, errors interfere with the reader's enjoyment of the story. Trying to read a story that is riddled with errors is like trying to carry on a meaningful conversation in the middle of an artillery range. You're reading along, hoping to get into the story, when BANG!

"Jane looked at Mark, and then at Fred. Suddenly, he hit her."

Wait, what? Who hit her? Was it Mark or Fred? What's going on?

"I really hope it's leg isn't hurt."

I really hope it is...leg...what? Oh, they mean "its leg." Got it. Now where was I?

"At this rate, he'll probably catch a venial disease."

A...what? Oh, ha-ha, they mean venereal disease. Someone didn't get much sex ed.

You get yanked out of the narrative. (If you notice an error in this post and go, "A-ha! She's so high and mighty, but she screws up, too!" you've just made my point for me, thank you.) The more exciting things are--it's an action scene, blood's flying everywhere--the worse it is, like hitting a speed bump when you're going 70 miles per hour. Not to mention that if the errors are bad enough, you literally cannot understand what the person is trying to say.

It's a problem once you publish, obviously. But I also think it's important that your work be at least somewhat polished if you're giving someone a draft to look over. I feel like it's a real waste of everyone's time if you give me something in hopes of getting meaningful feedback, and the only feedback I can give you is, "Please fix the grammar and spelling, and then I can actually focus on your story and tell you something of value."