...or interview witnesses/suspects or even provide direction to actual homicide detectives? I get it. You have to suspend a certain amount of belief to watch these shows; especially since they usually have their man/woman within a couple of days of the murder. I just find it strange that the forensic teams leads the actual investigation. That's all
shareSuspend disbelief...
shareIt's fiction...
shareSaying something is fiction isn't an excuse.
In the case of the CSI shows, the focus was intended to be on the forensic science (which, yes, wasn't always accurate and was almost always done too quickly.) Given that intent, there was little chance to engage the audience with a show restricted simply to the lab.
Now, I've seen the argument that they should have had regular officers for the street work and interviews and the CSI's for the lab work. And they all had "regular" officer involved. But any show can only have so many regular characters; both from an artistic and budgetary point of view.
So, they make the extrapolation to have the CSI's do interviews, carry guns and chase suspects. For these shows it is part of the suspension of disbelief necessary. Many shows have to do this to move the narrative.