Simple. Saves the cost of printing them. I just got Paramount's "Mean Girls" and it does not have an insert. Kinda silly since inserts usually contained one inportant piece of info - chapter stops. The studios are just taking a page from the software industry which doesn't include manuals or other documentation. So there goes my collection of "collectible inserts" that MGM used to trumpet as a "feature".
Speaking of Star Trek VI, I ripped the plastic on the case. I wish it was a normal case so I could just replace it. Damn security tape, this is not the first time I did some damage to case, but usually its just a small hole not a rip.