The .asp extension actually tells you nothing other than that the .asp extension was used. On the balance of probabilities, it's likely the case that the site runs on ASP classic on a Windows server, but it could as easily have been moved to, say, the LAMP stack configured (using httpd.conf or .htaccess) to invoke PHP when files bearing the .asp extension are requested. It's not a common thing to do, but it can be the easiest way to solve the link rot problem.
The snopes site is quite old. If they did move to a newer technology, it would be better for them to stick with their .asp extension so that they didn't have to change the URLs with redirects. They are well ranked across a lot of keywords - there is no upside for them to change their URL.
A buddy once had a client that decided their site needed to be in a different technology, "for browser compatibility". A quick remap later and the client was satisfied.
Summary/spoiler: It was to ensure the contract was read thoroughly.