One incentive might be that the "watch instantly" option is conditional on studio contracts, which are time-limited. I believe a number of movies lost their "w

One incentive might be that the "watch instantly" option is conditional on studio contracts, which are time-limited. I believe a number of movies lost their "watch instantly" option earlier this year for this reason. (It's a weak incentive, given that you can still order the discs, but it exists nonetheless.)