

It could also be that they're just lazy and can't be bothered to put newer drivers for such old systems, focusing their efforts in supporting just newer systems. It may be that Dell saw no significant improvements in the newer drivers that would affect your video card's performance, so they didn't bother making available a newer version for you. NVidia would most like apply most updates and most improvements in drivers for their newest generations of chips, and give lower priority to older generation cards, or only fixing major bugs or issues that are discovered (like let's say a very popular game not working well due to some optimization or bug in old driver and enough people complain about it)

Since then, nVidia released cards with several other architectures, like Pascal and now Turing (read it as different generations or families of chips) Your GTX 850M is a video card with a chip from 2014, based on the Maxwell architecture.
