Why Are People Still Creating RSS Feeds?

...instead of using the Atom syndication format?

Atom is a well-defined, general-purpose XML syndication format. RSS is fractured into four different versions. All the major feed readers have supported Atom for as long as I can remember, so why isn't its use more prevalent?

Worst of all are sites that provide feeds in both formats - what's the point?!

• UPDATE (18 August): Interestingly, this site itself is using Atom for its feeds rather than RSS.