So, for a few years now, it has been my intermittent habit that when I see an interesting site that has no RSS feed, I set one up on my server. Here is a list of all of them, minus the ones that have since set up their own proper RSSs (namely: Arts and Letters Daily, Alton Brown, The Cairo Times, Colin Gregory Palmer, David Byrne, Dykes To Watch Out For, Exile.RU, a few subsections of the New York Times, PBS Frontline, PBS Now, Helsingin Sanomat tuoreet, the LA Weekly, Mark Morford, Molly Ivins, George Monbiot, Mozilla extensions and themes, The OC Weekly, The Onion, the PBS NewsHour, Ray Ratto, Something Awful, The Smoking Gun, Viridian Notes, Watching Justice, Weebl and Bob, and Winscp releases).
And recently I set one up, and as usual emailed the site's webmaster and let him know. But then something weird happened: the webmaster wrote back and asked why I was setting up an RSS. That is, (he explained), not what is RSS for, but what's in it for me to set up an RSS for his site.
My reply to him was basically this:
I stumbled onto an essay on your site and then decided I wanted to keep track of what's new there; so I took a minute and set up an RSS generator to do that. And once a generator is set up for my amusement, it takes no real effort or expense to expose it for others to view too. So I encourage the world to look over my shoulder by watching anything/everything at http://interglacial.com/rss/ that amuses them.
I figure there's a sort of economy-of-scale involved: it's vastly easier for me to provide a hundred-and-something feeds than for even two of those site's maintainers to bother coding up their own RSS generators. This is especially true for all the nice comics authors that I make feeds for, because many of them are at wit's end just wrestling with making HTML wrappers for their images.
Anyway, other than my basically saying "I find these sites interesting and I hereby make it easier for RSS users to keep up to date with them", I have no grand plan. (In fact, I'm basically casting these RSSs into the void, because there's no good way to find out how many people actually read them. But now and then I randomly run into people online that say "I read a dozen of your feeds every day!".)