Some analysts have suggested that young people picked up on the use of so to start sentences precisely because it was cool techies that they had heard speaking in this way. If those geeky chaps prefaced their comments with so, it must a good thing to do, as it would make you sound clever, credible or intellectual, wouldn’t it?
Unfortunately, for many people, so has the opposite effect!
The principle reason that so is now used excessively is that there are so many ways to use it!
A verbal crutch
There are certain words that we all utilise as crutches when we are speaking, at least occasionally. They come in handy when we lose our train of thought or need a brief pause to think. These words include um and basically. The word so has now joined the list of these verbal crutches. But such handy words can be so useful that they are habit-forming. As so is often employed as a crutch, its inclusion in a sentence can be perceived as lazy. This is at least one of the reasons why so can be so very irritating.
Avoiding a straight answer
It has been suggested that so is often used to begin a sentence because it helps the speaker to avoid giving a straight answer. As discussed above, so has become a crutch word which enables the speaker to pause and that can be very useful when they are formulating a lie! In addition, the speaker could feel that they will sound more intelligent if they start their comment with so. It follows that they might believe the word will distract the listener from any lack of substance in their answer.