Blame indie bundles that give us rubbish games. Every time I buy an indie bundle, chances are it's because there's only one or two games in it that I'm interested in playing.
Join our Steam Community group if you haven't already and then you can give away the games that you don't want. I find that there's always someone who want a certain game.
Finish most of my games, but I do have a sizable backlog. A lot of the stuff on my list are older games that I pirated back in the day before I had a job. Bought them to atone for transgressions so to speak. Won't end up playing them again though.