Do we need to remember our manners ?

I don't know if  there is any better  way to get people being polite and I believe a lot of  people know the manners . The  question is: Why are some people  impolite?
 Most of them started to be rude because they don`t care anymore.  How is posible not to  remember manners when you see in a bus or in a  subway a pregnant woman standing while another person takes the place that was reservated for her? Well... we know that is not polite  but the truth is we don't care because we are too busy or we are overwhelmed by our problems ...unfortunately