Actually doing that is not all bad.. sometimes it's the smart thing to do, as you really don't have to finish every single game you play (just like with movies, tv shows, anime, books etc). i try something if it's not for me or something in it gameplay wise puts me off (like too much grinding etc) to the "unfinished garbage bin" it goes. Or i'll just watch a longplay/walkthrough from where i left it if i really want to see how it ends etc.
I think "unfinished" here means you'd like to keep playing it but get distracted by shiny new titles. It's fine to drop games you don't enjoy but I don't consider them "unfinished" because if you decide to dump it in the bin you're pretty much finished with it