My backing depends on the quilt and how I am going to bind it. Both of my children's graduation quilts had backs that matched the front because I put their school initials and graduation year in block on the back (large.) I also rolled over the back of my daughter's because that was the fabric I was using to bind it. Saved me making a separate binding.
Sometimes I match a color on the front with a solid backing, sometimes I just use muslin. I tend to back baby quilts with a softer fabric that can be cuddled.
Don't mind piecing the back, but I love the ease of the full width backing.
Hope some of that helps! Good luck.