What Happened to the Continuous Tense?

Why is it that just about no one says I am sitting or I am standing, or I was sitting or I was standing any more? Or just about any other continuous tense of any verb you can think of for that matter?  It's all I am sat, or I was sat, or I am stood, or I was stood, etc. etc. Even people who otherwise sound quite educated do it. In fact just about everyone seems to be doing it, both orally and in print, including in many of our finest organs.  

Why for God's sake?  If they had been George Formby would they have sung: I'm Leant on a Lampost at the Corner of the Street in Case a Certain Little Lady Comes By ?  Doesn't scan quite so well does it, quite apart from displaying ignorance of English grammar?  The only explanation I can think of for this and the countless other ways in which the depressing impoverishment of our language continues to accelerate is that grammar and style are no longer taught to our kids in school.  The notion  seems to be abroad that as long as what kids say or write is understandable, that's OK.  Don't correct the poor little dears in case you upset them or damage their confidence.  And anyway good grammar is really just posh middle class talk so it's discriminatory and offensive to suggest it is superior to chav talk.  In fact some seem to think its not only socially desirable but linguistically desirable to let kids make up their own grammar and style because that enriches our language.  

No it doesn't you clods.  It just makes them sound ignorant, not least to the millions of foreigners who speak and write far better English than they do, and it makes for prose and speech that are devoid of elegance and style and painful to listen to (the thousands of varied and interesting words and phrases that have been replaced in the speech of just about everyone in public life, especially at the BBC, by the words in terms of is another example of the same depressing trend).  

I suspect we are now well into stage two of the nuclear chain reaction, with most of the so-called English teachers in our schools being incapable of teaching good grammar or style because they haven't a clue what constitutes it themselves as a result of having been taught the same ideological junk in their own school days.

If you can get us out of this fine mess Mr Gove, you'll go down in history as one of our great political heroes .