If RSS was made with anything commercial in mind it would have to be selling offers and new products. How sensible would it be to have the latest properties in your price bracket updated everyday by RSS? How good would it be to have the latest holiday or flight offers flash up daily via an RSS feed? It would just take the pain away from trawling through poorly designed, slow loading sites and also ensure that people saw your companies proposition as soon as they were live rather than having to actually visit your site (which they may only have done a couple of weeks later, if at all).
Do BA offer this? no. Does Foxtons offer this? No. The question is why are all these companies so slow to grasp hold of this? I suspect the answer is that their agencies aren't keen to sell them something that isn't overtly creative.