Well, because Samsung makes hard drives and it looks suspicious seeing another hard drive manufacturer's hdd in there. Write codes? You have me on that one. I can use any brand hdd in my PC and it also writes
Understand DVRs are not at all like computers where the software is built with all kinds of drivers to run all kinds of different equipment. They have very little space to write drivers for the hardware and only write the bare minimum to make it work right. As they should. They have optimized their stuff to work with western digital av drives for a while now it seems, and adding in Samsung to the mix would widen what they have to code for. Will others work, sure, but are the drivers optimized, no, not in a DIRECTV machine. That's why they only recommend the wd av drives. I don't know if they have any segates in any new units or not, (haven't seen any) but its possible they have chosen to include two sets of drivers, but I don't see them going beyond two options ever anyway myself.
Plus, I am not sure Samsung makes a drive that will spec out against the wd av drives, that's not as much their forte. We are talking about drives running 24/7 and capable of writing and or reading up to 11 streams at once, all but one of which needs to be able to be hd av data.
And you are forgetting something else, DIRECTV probably can get one heck of a deal by buying all its drives from wd rather than Samsung and wd. And not one person knows based on marketing or packaging who is the maker of these units. This isn't a Samsung device. Its a DIRECTV device that Samsung assembles based in what DIRECTV wants and said to put in the unit.
Many companies build oem products for other companies. In fact almost all the big companies. Do you know how many actual different companies build the panels for plasm or led and LCD flat panels? No where near as many as the number of companies that sell them.