Purpose?
It came about from an email elsewhere about messing with the parameters of video card output under Linux, in order to write to the VBI lines and produce a teletext signal to the TV.
With the Amiga's native PAL output, you don't need a crazy adapter - if it is possible to write into the VBI.
The point? The only potential real world use I can think of, is distributing live updating text information internally to TVs, maybe in a hotel. But there doesn't need to be any real world use, right? It's just a fun thing to try and do.