Originally Posted by craigthemif

Because you can buy 5k points for $85 when the 40% bonus promo rolls around.

Save $100 on a room, use $85 of that to buy back the 5k points. $15 remains in your bank account... You also earn 650 points for spending $100 on a room instead of using points.

Of course there are multiple nuances, but that's the gist of the value proposition for those who can use the GC for a real $100 savings and for those who never max out buying points.