You need to be able to transcode for two reasons
1) You want to conserve bandwith
2) If your playback device can't play the media in question
I've got lots of stuff in 4K HDR which won't playback on everything I have and also is far too big a file to want to stream to something like an iPhone while on the train
Fair enough. This is a fair case for using transcoding. However you will find out that even after transcoding you won't be able to stream to your phone while on a train.