Originally Posted by Lux Flyer

This is not a feasible policy in the modern airline industry where incremental revenue from seat assignment purchases represents a sizeable chunk of revenue. Unless the seat next to you doesn't have any incremental value associated with it (which unless you are in the back of the plane, it does), the airline is risking giving away incremental revenue by blocking that seat. United brings in more incremental revenue from people paying for these seats you want blocked in a single day, then any individual GS is going to spend with them in a year.