Selling those sites without monetising them first, you're not going to get a great price for them. It's like the difference between selling a house and selling the land on which a house could be built. You have to think of what makes a site attractive to someone who is going to buy it - traffic, revenue and potential for more development. To make a site easy to sell, someone's going to have to do a lot of work, and they're not going to want to pay an awful lot of money before they sit down to do that work.