Weird Writing Habits

UPDATE: Guys, i don't care what i said, this book is AMAZEBALLS. Seriously, it's worth the terrible spelling.

Okay, i know the title is probably way off track, but it was the only thing i could think of.
I'm reading Blood Red Road by Moira Young, and one thing that really annoys me is the terrible grammar (i know it's deliberate) and the lack of quotation marks, HOW AM I SUPPOSED TO KNOW WHETHER THEY'RE SAYING ANYTHING HUH?

*cough cough*


But seeing this has got me thinking, why do these authors do it? What makes it worth the while to purposefully write it as if a five-year-old had?
Of course, the first thing you think is: Impact. By making the character barely literate, or unable to spell, you're emphasising a lack of education or this persons particular way of life. This can work sometimes, especially if you want to constantly remind people that in the world your characters live in, these things aren't important.

But, if you're a Grammar Nazi (a.k.a. Me) then you spend at least five minutes on each page, working out each word and re-spelling them in your head. After 100 pages, this makes you really crabby.
An example of this in Blood Red Road is 'I ain't afeared of nuthin', which i had to re-think into 'I am not afraid of anything'. God, what a waste of time.

Alright, sorry i'm rambling on, i know most people are looking to skim. And to be honest, in some cases this form of writing can work, like in the Chaos Walking Trilogy, where there is just enough to have an impact but not so much that you're tearing your hair out.
Anyways, what do you guys think? Do you find it interesting, or does the Grammar Nazi effect have you getting a migraine every time you read the book?

Think about it.
Imo <l:)>