Why is that inexplicable to you? Cunt is reserved as the worst of the worst. In Australia in my experience like 80% of the population still doesn't like the word. It's mostly just <40 year old blue-collar guys that like saying it constantly. And even though the meme is that cunt is our national word and we begin and end every sentence with it, if you walk up to a random guy in the street and say "g'day cunt" you'll still probably get punched in the mouth.
The very reason we (australia) started saying it so much was because it was shocking, and the most shocking word available. It didn't last long, the shock wore off pretty quickly and now it's basically just a way of say "hey i'm low class".
And before anybody gets offended by that last part, it really, really is. Think about it. You aren't gonna see geoffrey rush or hugh jackman casually dropping the C-bomb every 5 seconds, are you? Imagine being at a dinner date with cate blanchett and nicole kidman and saying "hey cunt, can you pass the salt?" Not gonna go well I dont think, and you know why.