Mine was a combination of not really having anywhere to display it, not playing 99% of it, not wanting to burden anyone else with getting rid of it, and figured I may as well let other people enjoy it. The official start of the cleanout was breaking up my Atari 2600 stuff, then followed with selling almost all of my TurboGrafx/PC Engine, Sega Saturn/CD, a large amount of NES/SNES, and most of my Atari 7800 stuff.
Still have a lot to sell off Atari-wise. Going to be going through consoles next.