I have long assumed that the principal reason for the taboos that have become part of religious beliefs was a form of social control, which contained what was once useful information for society. For example, Jews and Muslims have taboos against eating pork because they were unable to process it properly in a desert environment. Christians were able to remove this taboo because they had access to Roman technology.
In addition to useful information, therefore, it is likely that religious lessons were aimed at areas in which the audience for them were most delinquent. So, Confucianism in China and Korea has powerful filial piety principles because of the strong incentives to discard unwanted relatives during times of difficulty, Christianity emphasizes tolerance and doing unto others because of the (largely European) propensity to resort to violence and Islam bans alcohol because its members are unable to control themselves where drink is concerned.
And in Buddhism: one of the main concerns is that people should show ‘mindfulness,’ which is the opposite of mindlessness and concerns the degree to which people are aware of what is going on around them. I was reminded of this again this morning when, during my journey to work, I saw two instances of people nearly being run over by motor cycle or car (including the taxi in which I was travelling) purely because they did not look around (or anywhere) before walking across the road. In the first case, a woman walked in front of a motor cycle taxi that was so close to her that even if she did not look around (which she did not) then she surely must have been able to hear it.
To some extent, this may be explained by the family system in society: a great deal more emphasis is placed on family connections in East Asia than in most of the western world and this is correlated with lack of trust in non-family members. Since Thailand has a very low trust society (everybody believes everyone else is about to rip them off, one way or another), only family members can be trusted and, indeed, acknowledged. If non-family members are acknowledged in public places, then that means that social status issues arise and people must behave accordingly. Since people do not wish to do this all the time, they simply ignore everyone else as if they did not exist. This happens in other countries too – in Korea, the person who has not been introduced does not really exist.