This service is mainly suited for web shops and catalogs. When there is a large number of products, it's really not viable to do numerous updates by administering them through the backend. Instead, having them all in a spreadsheet allows for a quick and easy bulk updates regardless of the number of changes. Having ran a few web shops since 2005 until recently, this has proven time and again to be a huge time saver. The same goes for a large book catalog site with over 5,000 items, where the same method is used for adding new, and administering existing products.
As a shop owner or administrator, you receive at least monthly price lists from your supplier or suppliers. In my case there were six, with 2,500 to 10,000+ products each, with a couple coming daily. The main shop featured just over 6,500 products. That's a lot of data to be checked, and you probably have something in place to process changes. What my method allows me to do however, is much more:
I call it simply The Engine, and have built one for every shop and catalog I built and then administered long term. It's built and used by us only, and is an optional administration service we offer.