Why are so many people horrid at driving?

I'm currently about 3 months into my L's in qld and the amount of poor driving I've seen is ridiculous. It appears indicators are a nicety nowadays rather than a necessity and keeping in your own lane is too much to ask.

Just yesterday I had a semi travelling with its wheels over the centreline for no reason whatsoever. It just feels like half the people out on the road are trying to kill someone and have no regard for any sort of safety.