The benefits and reasons for using RSS are it solves a problem for people who regularly use the web. It allows you to easily stay informed by retrieving the latest content from the sites you are interested in. You save time by not needing to visit each site individually.
So you would add am RSS feed for an online store? for google's benefit? I may add one in this case. Thanks
Using the rss feeds visitors can receive updates and new contents of your sites in their email. It brings back visitors and search engines love the rss feeds too.
Seems like it mostly to be used for getting returning visitors. When subscribed visitors see an interesting post on rss chances are they will visit the site.