OP is getting a lot of hate but I can understand his point of view and I agree that lacking trophies subtracts from the replay value of a game.
Of course trophies add to the experience, and I dislike how people try to put them down, or blame the people who like them for all the problems in gaming. There is just no good argument against trophies - they are totally optional, they are extra challenges, and those who don't like or care can simply ignore them. Those who like trophy hunting, however, have all rights to complain about (lack of) a feature they like...
Uncharted 2 had the perfect DLC/trophy list. The Platinum was obtainable without a heavy multiplayer investment, while the DLC offered trophies for the online commited. I see no reason why Naughty Dog shouldn't add trophies to Uncharted 3 DLC. It won't affect the Platinum, and will keep people playing more.
The way I see it, no one has the right to blame someone for hunting trophies. What is the difference of replaying a game in a frustratingly high difficulty in a game without trophies, or grinding some matches for a trophy online? In both situations said person is having the fun they way he/she chose to, and really no one can judge what is fun (for some people suffering through an insanely punishing game is fun, for others collecting impossible trophies is fun...). In the end we are all just playing - trying to have fun under rules imposed by the developers. If doing those tasks wasn't any fun, we'd all just watch movies.
