I've always found Aberdeen quite good for manners. I'd say I have about a 90% "thank you" rate when I hold doors for people
As for blanking people, maybe people are just shy or anxious. I'm pretty shy and usually spend a second or two wondering whether a person would expect a hello, or whether they even remember me etc, then by the time I have a pathetic wee argument with myself they're past and I'm left wondering what the hell is wrong with me and thinking I should have just smiled and said hello. Every bloody time, I never learn.