I believe it is one problem. $$$$
Go to this link, and drill down to see what the production budget is for some of these movies. Some list it, some don't.
http://www.boxofficemojo.com/weekly/chart/?yr=2014&wk=14&p=.htm
you will see that the studios have to cough up a lot of money to make something that might end up being box office death.
Robert Rodriguez (Spy Kids, Sin City, etc.) made his first film (el mariachi) for $5,000 partially funded by farming himself out for medical experiments (he still has the biopsy scars to show from it). He ended up winning all sorts of awards and getting his work recognized by Hollywood.
If you are interested, I highly recommend watching the director's comments from the film el mariachi on DVD. He also wrote a book on the tale of how he filmed, cut and sold it. Very interesting. He did every thing CHEAP! I mean CHEAP!