I am currently on an NES kick, trying to play all the great games from that system is quite the task. I still have a stack of games on the Wii and PS3 I want to play and I'm always finding myself wanting to play some great game from the SNES/N64/PS1 or some older PC games. I've sold a few games in the past and have always regretted it - I will never sell consoles if I can help it.
However I game as a hobby for its own sake, I have very few friends that play video games, I rarely play multiplayer and simply play games that I find fun in their own right. That's why I don't want to sell my games/system (and also why I'm turned off by a large portion of games today) but I've found is not true for everyone or a lot of today's games. If competition and/or belonging is important to you, if you're largest priority is to play the newest, coolest games then I can see how selling older games/systems would make sense.