Groups - public/private

Why are the "groups" mixed up? It can say "public" on the main listing and when you pick it you can't see the discussions. If its public shouldn't you be able to see the group discussions with out joining the group first? Isn't that the definition of public?
I get that I can join the group to get access to the discussions but then I end up with 500 groups that I have to weed thru to delete if they are not of interest any longer.
Hell, you can even see the discussions on some groups that say "private". WTH?