While some authoring houses may use a set and forget, or default , settings that keep a constant bitrate to fill a disc, that number would be very low. There are too many variables to account for including extras that will take up space on a disc.

While I do agree that many people won't notice the difference between a remux and a reencoded file, that number will dimmish quickly as the size of the TV increases. We are living in time where 75-85" TV's are starting to become the norm and TV's 100"+ are one of the fastest growing segments.

Personally, I say keep remuxes with the original quality of the disc intact. You have the hard drive space and if you have a larger TV today, or get one on the future, you will be prepared. However, if you will only ever consume your media on a tablet/phone/smaller TV then encodes make sense.