Oh, and also, security. After the Sony hack several years ago, many film studios have severe restrictions on what they'll allow off-site. For upcoming unrelease

Oh, and also, security. After the Sony hack several years ago, many film studios have severe restrictions on what they'll allow off-site. For upcoming unreleased movies, many studios are overly protective of their IP and want to mitigate the chance of a leak as much as possible. Often times complying with those restrictions and auditing the entire process is enough to make on-site rendering more attractive.