Part of the reason WJBK is there is so that there is a balance and nonduplication of syndicated programming. If you picked WXYZ from Detroit, WTOL from Toledo and WGRZ from Buffalo, there is a chance that all 3 carry one or more syndicated programs - but with all stations from one market - you wouldn't see Wheel of Fortune on the American channels at once (for example). Look at it this way - WWJ's lack of local news probably balances WJBK's news (compared to other markets).
It's the end of the day... and maybe my brain has fried
... But could you please clarify this post so I can understand it better.
Let's assume, for the sake of argument, that Wheel/Jeopardy! aired on WDIV (NBC) Detroit, WTOL (CBS) Toledo, and WEWS (ABC) Cleveland. If a cable system carried those three stations, you would have the same programming on those three channels, plus whatever Canadian channels were carrying it. Of course, the U.S. stations get sim-subbed, but from the viewers' standpoint, there's a lack of choice when 4 channels on the lower end of the dial have the same shows at the same time.