what am i missing ... why run a S/390 platform with Fedora desktop?

I found this [link](http://s390.koji.fedoraproject.org/) for a group that is converting fedora RPM's to run on S/390 hardware. [Wikipedia](http://en.wikipedia.org/wiki/S390) tells me that the S/390 was made by IBM as a mainframe computer in the 1990's (and run out of service before 2000). So I have two questions: Why would you run a "standard desktop" OS on a (deprecated) mainframe? and are there any practical applications for a 1990's mainframe nowadays? The site seems to be pretty active, so I feel I must be missing something in its purpose.