what is the point of the Tanoby Chambers other than the unknowns???

Umm... just for the Unkowns. Thats their reason, to give you a place to catch Unkowns.

Yep. There are different kinds of unown in each chamber. example: You can catch O in the liptoo chamber.

The Tanoby Chambers and Tanoby Ruins give you a place to find the Unknown and pretty much to give the island a perk.

Each unown has its own chamber. Go to the back of any of the chambers. Note the colored dots on the pillars and the colored tiles on the top edge of screen. The colors of those are different for each chamber. You can catch the entire alphabet on each game. Some forms are rarer then others. I believe the ! and ? unown are the rarest. You catch ? in the first chamber(monean). A and B can also be caught there I think.