I don't have long enough arms to cut more than 24-30" vertically at the most. And if I am cutting for a big piece of fabric - say a one block wonder - I just move it along the board. when I trim a sandwiched quilt, I put two boards together and move slowly along the 72".
For me that would be like making my 48"x72" kitchen island a big wooden chopping board . I can only chop one batch of veggies at a time so the 24"x56" cutting board countertop with the built-in veggie sink is more than enough.
I guess I just miss the point. What should I be doing with all that board?