I cannot stand seeing the phrase "hence why" as in "the printer was down, hence why I wrote out my shopping list"
why is unnecessary!!! And I see it a LOT on the internet
I think "hence" and "hence why" are two different phrases. The first is when it is a logical conclusion. The second is used in a sarcastic way when if the person had just been paying attention, the logical conclusion would have been obvious.
"This is broken. Hence I pulled out my scissors to fix it."
"This is broken, let me pull out my scissors."
"You can't use that, it's broken."
"Yes, hence why I just pulled out my scissors."
It is still grammatically incorrect. If emphasis is needed, then "hence this is why" should be the phrase, not "hence why", which is blatantly wrong. Even "hence this is why" is largely redundant, but at least correct.
What annoys me more is when people say, "I could care less." The first few times I read it (I've only ever seen it online), I assumed it was a typo. Now I've learnt that some people actually just don't understand what they're typing. Every time I read it I have to translate it to its opposite in my head.
I've taken to using "I could care less" on occasion when it is possible that I could care less, but not by much. I see it as one degree of disdain less than "I couldn't care less."
However, when I use the phrase on its own, it's always spoken, and there's a slight emphasis on the word "could," with a fading off:
If it's written, I add a modifier, like "... but it would require heavy equipment."
(Count me as another who thinks "hence why" is ridiculous, "hence, this is why" is redundant , and that both versions should vanish permanently.)