Yes, there are reasons why fewer and fewer models are released from movies.
Corporate greed and the worry about pirate copies, etc.
Coprorations ask a lot of money from anybody that wants to use their designs & images, making it nearly impossible for a model maker to afford making one of those kits.
The few that have that much spare cash tend to be more along the lines of action toy and similar makers.
Seen it at some shows where the lawyers for studios like Warner, DC Comics, etc walk around and hand out C&D orders to dealers of garage kits that sculpted and cast kits based on a movie.