You are seeing it more and more and hearing it more and more because very few English-speakers give a tuppenny toss about speaking English well. Did you hear a BBC reporter saying it?
Present tense - I am sitting, you are sitting, he is sitting et cetera
Past tense, in fact, one of our many past tenses - I sat, you sat, he sat et cetera
They should be sitting there facing the front, at four years old, saying all of the tenses by rote, followed by the two times table. We'll never compete with the Poles for jobs if we don't get a bit of rigour into our education system.
As an English child in England I didn't learn to conjugate tenses until I went to big school and learned French and Latin, but I sometimes think it wouldn't have hurt to spend a little bit of school time talking about tenses in English.
Do you think "We was sat here" is worse than "I am sat here"?