If I'm bored with not much else to do and I really enjoyed the game, I don't mind running back through it to clean up some trophies and attempt the plat. I've never actually gotten a plat, though. lol Came close on Hotline Miami a few months back, but the last one wouldn't pop.

Yeah, trophy hunting is probably an exercise in futility, but if you love the game, why not? Good way to get the most bang for your buck, imo.

If I'm not mistaken PSNprofiles do check whether or not a person is cheating or using a shated account. I would assume that they'd double check the people at the top of the rankings to make sure that they're following the rules.

In your original post you ask, how do people find the time to platinum several games. I provide a answer to that question. 

NOT completing certain games kinda feels wrong to me,the most obvious exemple i can come up with on the spot is Donkey Kong Country,isn't the goal of the game to explore the levels and discover secrets as much as beating the level? Honestly if you play DKC and rush levels i don't even know why you would play that game but that's just me.

Trophy Hunters/Completionist feel the same way about playing a game that they're not gonna complete. Why even play God of War if you're gonna play it on Easy? Getting a platinum feels like you played a game the way it was meant te be played.

Pretty indifferent about them. It is neat at times to check stats on how many people even finish the games. Not that many apparently.