I came across an old thread started by tebo53 entitled "politeness and manners" which, interestingly, has been locked otherwise I would have added to it.
I've noticed the lack of common courtesy from some people.
Insults and name calling - the sort of thing that you might expect in a playground.
No please or thank you with a question.
A single punctuation mark used as a reply.
No reply, no acknowledgement at all.
I don't expect someone to be grateful for the rest of their lives just because I've told them where the bus stop is, but a "thanks" or a thumbs up would at least let me know they've seen my answer, understand it and are happy with it. But to just ignore it exposes, I suppose, the root of the word ignorance.