Who wouldn't want to see photos of their puppy growing up? When I had puppies for sale I had their photos posted on my website and the new owners where also sent new progress reports and photos every Sunday. Everyone loved it! In fact one new owner even made a puppy growing up photo album - an adorable item she never could have had if I had not taken the photos in the first place.
Also, you want to try to find owners for the puppies and you want to have the time to do so. At 10-12 weeks of age you dont want to go out and find just anyone to be your puppies forever home. Placing puppies on a website gives you those 10-12 weeks (or longer if you take names for future litters) to find the best homes you can for your babies.