In the mainstream video business, this model works well because all new movies are released on Tuesdays (unless there is a special marketing reason for a specific title to be released on a given date). Whether from a manufacturer or distributor, a video store will typically receive the movies for the following Tuesday on Thursday or Friday. This will give them time to get everything tagged and entered into their computers to be put on the shelves on Tuesday morning.
With adult product, different movies are released every day. Some companies, that release multiple titles a week, do so on multiple days (Evil Angel, West Coast, Anabolic...).
For websites, title information has to be entered, box covers need to be scanned, etc... before the movie can be added to the site. In Adult DVD Empire's case, it seems that they are now taking the time to review titles before they put them on the site. That also takes a while to do.
I also think that you will see that, in many cases, the sites that do a better job at getting titles onto their site are the ones for whom Internet DVD sales (and possibly distribution) is their only business. The ones who also have a brick & mortar store have other things going on that can negatively impact the operation of their Internet business.
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