[greymule]

Do all of you people walk down the street correcting people's grammar?

When walking down the street, no, but all day at a desk, yes. A lot of people give a damn and are willing to pay to ensure that the writing they submit (an academic thesis, a report to government, a business proposal) is correct in grammar and usage.

Unfortunately, I can't simply turn the machine off in everyday life. Every error I hear registers on my consciousness. But I stopped gratuitously giving advice after suffering a stab wound from a fork after correcting my mother-in-law (memento, not momento).