What is it with all the sign offs?

I have been reading with some interest the various threads etc and I have found them quite informative and insightful. However, what is it with all the sign offs? 'Lets keep dancing', 'stuff a mushroom' 'the rocking jedi badger', 'Absit invidia', am I missing something? Why are they all so 'wacky'? Nothing against those that use them of course, just a 'wondering'.