The rationale is because it NEEDS to be done. It don't just look for updates to the system software and download the guide. It also is an opportunity for the box to do some housekeeping of the hard drive and make sure it's working properly. For example, I did a mass transfer of items from one EHD to the internal drive and then to another larger EHD. The next day I noticed that the available space was slightly different from the night before after I had finished transferring. When my Hopper did it's system update, it also cleaned up some fragmentation and opened up more space for it to use for recordings. On prior system software on other Dish boxes, they did allow you to set things like when nightly updates would run, but slowly they have been limiting or taking that ability away all together. Because getting the nightly download and running maintenance on the system is so important.