spoken discourse

My mom was quite appalled the other day when she overheard my end of the telephone conversation i was having with my friend. it went something like this:

Ringring..

Me: Later, 5, bishan, k?
Friend: k, set.

End.

She was lamenting on how politeness and social etiquette has been lost in my generation. Hahaha, well i guess i little hello or smth would have been nice, but my friend and i have known each other for years and i guess we didnt require all this unnecessary 'politeness cues'. Its not that we are rude to each other, its more of the result of our friendship and the sense of comfort around each other. We do exchange our pleases' and thankyous, but somehow our hellos and goodbyes were lost somewhere as our friendship grew closer.
On a sidenote, my friend does not like to say 'bye' or 'goodbye', rather he prefers 'see you' or 'talk to you soon'. haha, its a thing of his, like he thinks saying goodbye is like a bad omen.

Anyway, so yes, telephone greetings. In a professional setting the conversation would usually be filled with social etiquette-following mannerisms. An extensive amount of thankyous, pleases', ibegyourpardons and whatnots. Why do we follow such rules when conversing? Its all part of the social conditioning we have been through. it is through this that we come to perceive actions of speech as being 'polite' or 'impolite'. What IS being polite? i think the line between the two extremities differ across cultures, and ultimately the universal 'hello, how are you' is the safest way to go!