I've had the same thought. In CSI, where most episodes have two plots, there isn't enough time for anything but the tightest scripting and plotting (it's this necessary discipline that made CSI stand out from the competition back in 2000). In NCIS, about half of each episode is devoted to humorous banter among the regulars, with a similar effect on the detection plot.

Another consequence of the CSI formula is that there's not enough screen time for a courtroom scene, so each plot has to end with the guilty party waiving his or her rights under the fifth amendment and confessing, destroying any lingering shreds of plausibility.