True enough. Of course a show like The First 48 isn't going to concentrate on the cases that take a long time to solve or even go cold for a few years. But no matter what show it is, in comparison real life cases are more tedious, slow, and the finer details are not known until the legal portion begins (whether that's a trial or plea deal).
And the general public will always feel left out, like their favorite episode of CSI is on and someone unplugged the TV.
I'm surprised when people are surprised that LE knows more than they tell. I mean...this is not some new thing. Ever watch old Dragnet episodes from the 60's? Even fictional character Jack Friday kept information close to the vest. That's a given.