The beauty of buying kits is the fabric selection. I live in an area where fabric selection is poor and to spend hours and hours picking out fabrics online just isn't feasible as too many of them are not accurate in color. That is why I have a stash.
I have bought only 1 kit and it was done solely for the array of fabric. They did a much better job of color selection than I ever could. I had plenty of fabric to accommodate my mistakes. Yes, I paid way more for the kit than I would have for the fabric, but I also saved myself hours and hours of stress time in trying to select fabric. To me, it was a win-win.