It's all about getting the rights for the movies. B movie crap, pretty easy because they are looking for any distibution channel available. Blockbusters hits and big studio movies, not so much. For physical media, I believe they have to obtain the right to rent and then purchase large lots of the movies at a discounted price for rental. Redbox being relatively new, probably doesn't get first crack at a lot of these due to other companies wanting them exclusively. Netflix has been on the decline recently (as far as the streaming service goes) because of losing the rights of several different studios and subscription cable channels.
"Once more into the fray. Into the last good fight I'll ever know. Live and die this day. Live and die this day."