IMHO, it's all about the variety. I cannot find 40 coordinating fabrics all that easily, not to mention the cost of my time. Now, I do enjoy the "hunt"...finding just the right fabrics to go with my focus fabric, but there is a lot time involved, and there is the expense and storage of all the left-over fabrics when you purchase quarter or half yard cuts or more for quilts you are making.
My daughter does not have the time, money or space that I am blessed to have, so I have encouraged her to use pre-cuts so she can get right to her piecing and quilting. Plus, there are great patterns and books designed for pre-cuts now. How wonderful that we quilters have so many options!