I think the biggest reason is that the actors were allowed to act together. Modern movies use so many digital effects that actors aren't even on set together sometimes. It's hard to have the same emotions looking at a green screen and a guy in a morph suit.
Just for the first one, right? I remember Ian Mckellen had a breakdown on set because he was sitting in front of the table at Bag End with nothing around him but green screen and was struggling without any other actors.