You're right with your statement if you are not 100% sure you wanna go on this trip.
But if you do know you will, you can sometimes get very good rates, even if the hotel is sold-out on regular rates because travelocity buys a certain amount of rooms.
It's all depending on your travel plans/needs - and a travelocity value rate is roughly the same as a (more or less heavily) restricted plane ticket.