The only time I've had this offered to me was earlier this year when I was flying jfk-nrt-sin. Our jfk-nrt leg had a broken sensor on the ground so we had to sit on the plane for 3 hours while it was getting fixed. I only had a 2.5 hour layover so was faced with missing the last flight to Singapore. Delta reserved me a seat on a Singapore air A380 though upon landing they announced they were holding the Delta flight as enough people were connecting it was worth delaying the flight an hour for us to all catch it.