I should point out that the
90% I used was an out-of-my-ass value. What I meant was "Usually not, but sometimes yes", which I thought would be sufficiently illustrated by
90%, so that I wouldn't have to use English to explain English, especially considering your question was about the words I'd have to use to explain them.
Paul: What's your favourite drink?
Helen: Hot chocolate! But I sometimes drink coffee.
Sarah (Helen's best friend, looking shocked): What?! Excuse me, but you don't sometimes drink coffee. You drink it pretty much all day, every day!
A: "You sometimes drink coffee, don't you?"
B: "I don't
sometimes drink coffee. I
always drink it. You will rarely find me without a cup of coffee next to me."
This reminds me that
you've already asked about using sometimes like that. some half a year ago. I even gave you a very similar example of how one might want to use
sometimes after, not before,
don't.
G: I've heard you sometimes read in the evening, S.
S: No, I don't sometimes read in the evening. I always read in the evening.
You'd expect noticeable emphasis on sometimes and always.
I guess this is why textbooks usually avoid talking about this word order and recommend not using it altogether. Sentences where adverbs of frequency are positioned after a negation are very peculiar and can mean various things, depending on what the context is, and a learner is very likely to mess it up. It's easier to just tell a learner that using it is unnatural and call it a day.
The key thing is to understand what is being negated—the frequency or the activity. If the adverb is positioned after the negation, it's the frequency that's being negated.
A: "Do you
always do your homework?"
B: "No, not
always. I don't
always do my homework. I only
usually do my homework because I sometimes feel too lazy to do it."
Doing your homework doesn't happen
always; it happens
usually. It's the frequency that is being negated, not the activity itself. You do your homework, just
not always. If you want to negate the activity itself, you need to position the adverb before the negation.
C: "I usually don't do my homework. I don't have time for it."
Here, we learn what usually happens—not doing your homework. Most of the time, you don't do it. The frequency isn't being negated here; the activity is.
Now, while the sentence below is technically correct, it's extremely unlikely to be used by a native speaker...
D: "I always don't do my homework."
...because a much, much simpler way to convey the same message is available—changing the adverb of frequency...
D*: "I never do my homework."
...and that's how it usually works in real-life, everyday English. We use the simplest sentences that will do the job, so that nobody has to analyze and think what we mean.
However, sometimes, you might want to use an unusual sentence, not because it's more natural or easier to understand, but because it draws the reader's attention towards it, or maybe because the issue is so complex that it demands using a very specific, niche sentence structure to fully illustrate how complex it is.
While we'd love to live in a perfect world where family means everything and everyone's a saint, it's pretty obvious that everyone
at least sometimes hates their parents. That's not what's being discussed. What we're talking about is why someone doesn't
sometimes hate their parents.
E: "Wait... you're telling me you don't sometimes hate your parents? How is that possible?! Everyone sometimes hates their parents!"
