Why? So you can say you were there and part of it. Its like a party rave basically just with ships. There is some strategy at the top end but really its an excuse to blow billions of isk in a few hours for the sake of it (and maybe a bit of territorial control). Those with the most isk and numbers win the day normally.
You have to remember that with this, its all done via Teamspeak as well. Once your ships gone "phoof!" you end up sitting on the side lines chatting rubbish or popping (podding) yourself to a cryovat to get a new body and ship to get back into it. Its also a place to show off all those skills you've spent years training in via Cap ships and titans.
Some find it fun.
But you've seen the video? It looks like a shoal of fish, covered with an mikado.
