Currently, one can exchange points into miles but not the other way around. When one exchange points for miles, Marriott would have to actually buy miles from the airline. What if Marriott also allows members to exchange miles for points, but at a lower exchange ratio, say 1 for 1? I think many members will take advantage of this offer so that Marriott no longer has to spend money to buy miles from the airline. And they don't have issue new points for those miles either because whenever someone exchange points for miles, the exchange ratio is more like 3 to 1 and they make 200% profit between those 2-way exchanges. Why haven't they thought about this?
member 1: 75000 points -> 25000 miles
member 2: 25000 miles -> 25000 points
Net for Marriott: 0 miles, 50000 points in profit.