My wife pays all the bills in our house, so I don't write checks. I don't think I have written a check in a store in the last decade, certainly not in this millennium. But I do look out for people who still write checks. I live in Lancaster County PA, so people really do. In grocery stores the best way to avoid a check writer is by going to the automated check out line. No one who writes checks in public would be in that line.
Just now I am sitting in the Apple store waiting for my appointment with a Genius (the repair guys in the Apple store). While waiting in the Apple line--seated at a stool with my laptop using their WiFi--I saw a guy at the Genius bar paying for something his teenage son got repaired. The guy was writing a check!! First time for everything. I have never seen a check written in an Apple store.