I don't think special effects 'fool' anybody these days, what with making-of documentaries and coffee-table books everywhere. It's become part of the standard promotional strategy: "Look how much work we put into creating this stuff!" If there are still any magicians who guard their secrets, we don't know who they are.
But to answer your question, I think contemporary filmmakers go for CGI for two reasons: (A) It's perceived as more efficient and less expensive, and (B) it's the fashion. You're not big-league if you can't make your movie the way the big guys do.