Basic manners, the lack of.
Saying 'please' and 'thank you' was drummed into me as a kid, clearly half of these ignorant bastards today didn't.
Just nipped out to Tesco on my lunch and as I went to walk out, I stood aside for two young girls to enter, saying "sorry" as I did. They didn't even acknowledge me or utter a word, instead I'm stood there like a chump wondering why I even apologised in the first place.