Or they do realize it, but since it's not their pet peeve, they don't care.
It's all a matter of fact and opinion. There are some pet peeves we've talked about on here, which, in fact, constitute poor writing. Poor grammar, for instance. No expert on writing will ever tell you it's okay to publish something that is chock full of grammar errors, unless they're there intentionally as part of a character's own writing or dialect or something, or that it's okay to write a novel that is all one paragraph.
But a lot of the other things we complain about - banners, song lyrics, lengthy description, etc. - are just a matter of opinion. There are bestselling, highly-regarded, published novelists who use lyrics in their books and write lengthy, wordy descriptions. And banners are the online equivalent to the cover of a book. Sure, as a writer, you might want to take the opinions of other writers and your own readers into consideration. .. but when it all comes down to it, you need to do what you feel fits your story and your style the best. Our styles and tastes are all different, so definitely, one person's pet peeve may be another person's love.
Still funny to see what drives everyone nuts though LOL.