Because it's a great way to keep others up to date on your research. Using BibDesk's RSS features can help you do this with a minimum of extra work because you only have to keep your bibliography updated, and BibDesk will generate the RSS files for you.
By posting an RSS file generated by BibDesk, you can allow others to keep posted on your research. If someone subscribes to your papers list, they will notice in their news aggregator when you post an updated version. They will notice if you change an entry as well as if you add new entries. All you have to do when you want to update your RSS feed is to export the bibTeX file using BibDesk and replace the old version on your web server with the new one.
You can also use RSS to keep a list of papers you want your colleagues or students to read.
As more people doing interesting research use RSS to publish their papers (and recommendations of papers), you will be able to stay on top of more new research by using an aggregator to notice new publications.
This is much more efficient than trying to keep track of conference proceedings and journals in paper form!
NOTE: It's important to note that subscription doesn't require any resources from the person who is providing the feed. An application called a news aggregator periodically fetches the RSS file you post, and checks it for new items. So, as long as you post an RSS file somewhere accessible by http, people can subscribe to it! (You can also use the usual password protection for files via http to restrict the people who can subscribe, but that's outside the scope of this note. Ask your webmaster.)
Here is a short list of aggregators available for Mac OS X:
BibDesk will output RSS using the "Export to RSS..." command in the File menu.
I won't cover this part of these tools here - other websites do a fine job.
Written 2002, Michael McCracken - contact me with comments.