I for one am glad they removed that temptation for me to get ripped off. I had about 70% garbage rate on random sellers. Known ones about 50%. 99% some kind of annoying flaw.
Nothing to do with Netflix or the internet (although I'm sure it is true less people are buying DVDs). As one person above states, the DVD sellers (as well as the sunglasses sellers) have been the focus of a huge crackdown, particularly around Once. There were lots in Caballito where we are but now are none expect in the designated areas. One day they were allowed to sell on the street, the next they were shut down.
There are quite a few DVD shops in Olivos and Martinez either in small galerias or down backstreets. They must be selling or they wouldn't exist and many also sell games on DVD, although with DRM being so tough nowadays, most games are digital download only today.