"So" - a little, annoying, but defensible word

So, the little word "so" is apparently becoming a bit of a bugbear for some people.
I refer to the use of the word "so" at the beginning of a sentence or explanation or story. I don't think anyone objects to its use within a sentence as a conjunction or "discourse connective" - along with words like "and", "or", "but", "because", etc. In this context, it means "therefore" or "with the result that" or "in order that". Neither are people objecting to its use as an adverb, meaning "to such a great extent". In these contexts, it is a terse and economical alternative to a much longer phrase.
What people are complaining about is the use of "so" at the start of a sentence, where it does not relate to anything that has gone before. In this context, it is known as a "discourse marker", other examples being "oh", "well", "now", "then", "you know" and "I mean", and it has to be admitted that they don't actually add anything to the substance of the sentence. They are a kind of conversational affectation, I suppose.
Now (see what I did there?), it has to be said that most of the people who are doing the complaining are Brits. I am aware that I use it quite a lot myself - me, who would never consent to intersperse extraneous "like"s into my conversation! - and when I visit family in England it has been commented upon. It is clearly something I have picked up in Canada, and I have noticed many times my friends and acquaintances here using it (and, I must confess, it has never particularly annoyed me).
I kind of see it as a way of marking the beginning of a story or explanation or personal narrative. It sets the stage for an extended conversational interlude or monologue or even a snippet of gossip. It gathers the attention of the other person(s), and it prepares them for a shift or a new topic in the conversation. "So" - shifts in position, leans forwards confidentially - "this is the way I see it..." So (in the conjunctional sense), you could say that it does serve a purpose of sorts. But equally, I have to admit, most times it could be omitted with nothing lost. I'm not convinced, though, that it really merits the complaints of an irate British public (c.f. "get a life").