The quilt top I have on my LA now is 117" square. Since extra fabric is needed all around, the 118" backing still wouldn't be wide enough. But... if a quilt is 110", then 118" would mean not having to piece the backing, so it would be very useful.
That said, if I'm making a scrappy quilt top then I usually piece my backs anyway, using a variety of fabrics. I get rid of large scraps that way, and if the front is scrappy it seems only right that the back should be scrappy too.