MLB.tv blackouts and market restrictions help

I am from the Chicago area and I understand why Cubs and Sox games are blacked out, as they are aired through my cable provider.

What I do not understand is why Milwaukee Brewers and St. Louis Cardinals games are blacked out. I have no immediate access to them through my cable provider.

This is news to me as I just moved back home for summer and in my college town only the Chicago teams were blacked out.

Any explanation will be greatly appreciated. I am not upset as there are still ways to watch the games if I really wanted to, I just want to know why games are blacked out while not being aired through my cable provider.

Thanks!