I dont think its really a question of 'please' and 'thank-you'. Politeness comes in many forms. I've tryed explaining to my mum this concept. I tend not to use please and thank-you but I show my appreciation and gratitude in other ways. On the internet it can be expressed by
etc.
My mother often asks me why I dont say hello to my friends. Instead we nod and smile at each other. which to us is a visual form of politeness. The problem comes when the older generation think we are so rude, but we're not its just the way we express things are different to them.