"It is about Patsy Cline and it is about Roy Orbison, but it's also about sound dynamics and actual physics," she said. "Reverb is the sound of sound echoing in a room, and that reverb goes up or down depending on how loud or soft you sing. It's kind of like the importance of having breathing in between words: You want to hear the space you're in, and reverb makes it more alive, makes it breathe more."
I agree with her to an extent. Records had more reverb on them in the 1960s and 70s, generally because producers generally kept microphones at a certain distance from the vocalist's mouth. Somewhere along the way it went out of fashion as production values improved, and "close miking" became the norm. This record producers' web site has an explanation:
Question number 1 is why use reverb at all?
The reason reverb is virtually a necessity is because of the current practice of close miking. Oddly enough, close miking has not always been the norm. It took innovative producer Joe Meek to discover that putting the microphones much closer than the then accepted distance gave a much more exciting sound. But close miking deprives the sound of its natural reverberation, so the artificial variety is used to compensate.
At this point it is easy to see why we use reverb. But there is more to it than that - reverb just sounds nice. There is some instinct inside us to prefer a luxuriant aural environment, just as we prefer a luxuriantly soft sofa to a hard bench.
Of course, the reverb that we hear on these recordings is artifically produced through effects processing -- not through simply pushing the microphone back six inches. So Neko Case's comment above might be a little... artificial.
(Incidentally, one place where the use of excesive reverb is actually really grating to my ears is old Hindi music. Sometimes Lata Mangeshkar's voice, high-pitched to begin with, is really badly distorted.)