Because most people don't realize, because they don't read the ToS from those various digital downloaders, is that they usually set a time limit on how long they will make digital downloads available from their server(s). EA's used to be 2 years but may have changed. Considering that I have played Sims for about 10 years (Everquest for even longer), any digital downloads would have long since expired. The first one I remember them offering was in 2005 or 2006, their Holiday expansion pack for the Sims. They may continue to offer it out of the goodness of their hearts (I don't know), it is not something I can count on. Having a box that I can install onto my 10th computer works just great for me.
I'm glad that you are happy with your DD but personally I would rather have a "hard copy" in my hands and not have to worry about receiving my item from a third party in the future. It is the same reason I don't use Amazon's Cloud drive to store my music, or iTunes, or any of those other places you can buy digital stuff. I can buy a hard copy of most stuff and convert it to a digital format myself.