My guess would be that this is DRM related. It probably became very difficult to limit or explain the limit per account. When little Johnny with a separate profile installed the Watch Now feature on 5 of his friends' computers then Dad would be upset with Netflix when he called up trying to make his new Roku work. Or worse, the profiles where allowing people to get around the Watch Now limits. I don't know what the limits are but you can bet that the movie studios require them. With Netflix's push into streamed content, anything that gets in the way is likely to be cannibalized.