Think of the convenience to have all your favorite "Best of" looks, right at your fingertips.
Here are a few additional reasons why we feel this is a good practice...
1. It's a great way to present your portfolio along with various options to a client, and having them chose the look of the end result, giving them the sense of participation, and then easily reproducing the EXACT same lighting they chose.
2. When you have large projects that require you to shoot over several weeks, and need a uniform look. There's no better way than to document as much information as possible, and keeping it on record. That way you can change your set-up for other shoots, and can always come back to the original look for that long-term project.
There are a few systems that work online, but personally, I prefer the type that you download a .PSD file and work in Photoshop.