pacman vitamin

In the late 90's early 2000's I collected 2600 games. I would stop at a local thrift store once a week and there was always some titles available. At a minimum it would be the common games (Pac-Man, Combat, etc), but it often included suprises like boxed games, colecovision or intelivision titles. I recently have been back in the thrift stores on a fairly regular basis and out of curiousity stop to look at the video games. I have yet to see an atari cart, and have seen only a handful of NES, SNES or Sega games. Is this fairly common across the US (less games showing in places that used to have a lot)? When did it start and is there an underlying factor outside of the inventory hidden in people's houses just slowly drying up? I am interested to hear what the Atari world at large thinks.