There is either a demand on the item, OR a sequel or something is coming out where people will want to go back and play the originals.
Even if there isn't a demand they like to prepare for a possible one.
Take Halo 3, it is now 20$ instead of 5$. Maybe there is a demand and maybe there isn't I imagine most people who want it have it by now, but because of Halo 4 it is gone up 400% in price. Doesn't mean tons of people are buying it, but the demand for Halo 4 made Halo 3 rise.
What did the aldehyde say when it found the carboxylic acid hiding? "oic Acid!" har har har- Deathx113