I believe in manners, when my kids were little I would get them in the "habit" of saying excuse me and thank you with sort of jokes:
If they would say excuse me I would say with a wide eyed look "squeeze you, why I hardly even know you" and they would think that was so funny, which made them want to say it more often.
and for Thank you I would do the same look and say "WHAT 10 Q ????"" and one time my little one looked at me and said Mom say that 10 Q stuff really fast and you will understand what I am saying!!!!!