Love that this thread happens when I'm finally playing the FFXII:ZA remaster, because the original Final Fantasy 12 on PS2 is what set me on my trophy hunting ways (casual as they are). By the end of my first playthrough I cared more about filling the Sky Pirate's Den than pretty much anything else in the game.
The PS3 ping was and still is incredibly satisfying to hear pop and I can't wait to get me a new dualshock 3 so I can get back to that.
I also don't have a lot of extra money to spend on games, especially not new releases, so 'Helps me save money by purchasing less games but enjoying the ones I have for a longer period of time' is a huge thing for me.
Otherwise, there's just something really satisfying to me about completing tasks.