The delegation happens in any way, since the node doesn’t get a full file. So the work is already done on the satellite. Also storj already allows HTTP Range requests, so I can already retrieve part of a file if I want to.
The idea would be to get closer to the recommended segment size of 60MB. This would mostly benefit the customer as he would not pay for so many segments. If we are taking a website as an example you’ll have lots of really small files 10kb or smaller, some images which are just around 300kb. The small files may even stay on a satellite in meta data already. Packing it all together into one file you would maybe have 20 MB, this can be properly distributed to the nodes.
As for video providers, the splitting has indirectly to do with performance. It is also done to optimize the bitrate to the connection speed you have. In case your connection suddenly gets slow the player can decide to load some parts with a lower bitrate such that your playback doesn’t get disrupted.
The blob would not contradict with this. One thing is how the data is stores, another how the data is retrieved. I can still retrieve chunks of video, but the data can still be stored as a blob. As a user you won’t notice.