Not a filmmaker, but I imagine the same reason why a lot of software comes out in English first, and localized versions later. It's a lot of work to localize, t

Not a filmmaker, but I imagine the same reason why a lot of software comes out in English first, and localized versions later. It's a lot of work to localize, the work is often outsourced, and for design-heavy things the amount of internal changes even during late-stages of a project can be really high - too high to be worth involving the localizers at that point. So you wait until everything is done and out the door before bringing in localization to actually do their thing.