Well I got you. If I skip (whether intentionally or forgetfully) some common social practices, then people would think I'm weird; i.e, if you're eating in front of somebody then offering him to eat with you is considered something called 'courtesy'. If I avoid these common social practices, then people might feel 'weird' about me, although they won't reveal it to me, but its normal that they feel that way. Some people are natural in dealing social situations, but I'm not.

I think these formal behaviors are widely practiced, despite of religious/social/racial variations. And reality is, people do expect these formal behaviors in social situations. Some people are natural in doing these, while some others feel uncomfortable/find it difficult at these.