Grissom at the end

It seems to be the trend when a series gets rebooted that a prominent character from the original seasons doesn’t make a (significant) appearance until the end of the first episode of the rebooted season. It happened tonight with Grissom in this episode and I remember the same thing occurred a few years ago with The Smoking Man on the first rebooted season of the X-Files and I think JR in the rebooted Dallas and (real) Cooper in the rebooted Twin Peaks if memory serves me correctly. Why do creators choose to take this approach when the audience usually knows going in that the character is returning.