Sometimes verbal shorthand allows use of otherwise foul language as you rightly point out. It's becoming more acceptable I think over time, what with social media now rampant and text lingo being to the fore of many younger minds I can't see it stopping.
I don't mind the occasional BS or Sweet F.A. depending on the situation at hand but too much does get my goat eventually.
As to the reasons - well, I guess language is always evolving and adapting and that I do find a wonderful thing. English is big enough to take whatever is thrown at it and come back as healthy as ever, despite the dumb-downs and acronyms and what have you.